Jered Weaver's injury and its impact on the AL playoff picture

The Angels are making a late surge but have lost Jered Weaver temporarily after he was hit by a line drive. (US Presswire) On Thursday, the Angels announced

The Angels are making a late surge but have lost Jered Weaver temporarily after he was hit by a line drive. (US Presswire)

On Thursday, the Angels announced that Jered Weaver will miss his turn in the rotation this weekend. The team's ace was struck in the right shoulder by a Dustin Ackley line drive on Sunday, and a subsequent examination by Dr. Lewis Yocum revealed that Weaver was suffering from biceps tendinitis, which may be to blame for his allowing 17 earned runs across his past 22 1/3 innings, bumping his ERA from 2.22 to 2.86, likely pushing him out of contention for the AL Cy Young award. Manager Mike Scioscia has set up his rotation so that Weaver could take the ball this coming Tuesday, but they won't make a final decision about that plan for a few days.

The injury comes amid a rebound in which the Angels have won eight out of nine and 12 out of 15 following a stretch in which they had gone 7-15; even so, they now find themselves eight games off the pace in the AL West, and three games back in the wild-card hunt. The team's vaunted rotation — Weaver, C.J. Wilson, Zack Greinke, Dan Haren and Ervin Santana — was lit for a 5.88 ERA and 1.7 homers per nine while delivering just nine quality starts out of 22 in that latter span; nine times, their starters failed to pitch six innings, taxing a bullpen that was scorched for a 5.68 ERA in August. In their last 15 games, the starters have trimmed their ERA to 3.19, with nine quality starts.

The underachievement of the Angels' rotation has been one of the season's bigger surprises. Wilson, signed as a free agent over the winter, has been roughed up for a 6.33 EA in 11 second half starts. Greinke, acquired from Milwaukee just prior to the trade deadline, has shaken off a streak of four straight non-quality starts, but his ERA since being dealt is 4.36. Haren has battled back woes and seen his ERA rise to 4.46, while Santana has been the majors' most gopher-prone starter, yielding 1.9 homers per nine en route to a 5.32 ERA.

According to the Baseball Prospectus Playoffs Odds Report, the Angels still have a 45.8 percent chance at reaching the postseason, roughly on par with the estimates for the A's (46.8 percent), Orioles (48.2 percent), Tigers (50.6 percent), and Rays (56.5 percent), albeit with the lowest likelihood of any of those teams to win the division (1.7 percent). If they can make it to the playoffs — and if Weaver can recover — their rotation, for all of its flaws, still stacks up reasonably well relative to the other contenders. As I did with the Nationals' rotation earlier this week, I have employed a model based on some work by Baseball Prospectus' Nate Silver years ago, using an ERA estimator (Fielding Independent Pitching, a better projector of a pitcher's performance going forward than actual ERA) and a historical distribution of postseason starts among a team's top four starters; Silver found that teams’ aces took 31 percent, with number twos at 28 percent, threes at 23 percent, and fours at 18 percent. Along with that, I have factored in each pitcher's innings per start, and constant levels of bullpen, offensive and defensive support based on the team's performance to date, plugging the numbers into the Pythagorean formula to estimate each team's "support-neutral" winning percentage over a maximum 19-game playoff run (one five-game series and two seven-game ones; I have not specifically accounted for the wild-card game in my model). While all of the projected winning percentages are above .500 — these are potential playoff teams, after all — some will inevitably fall short of that mark in October.

Ranked by projected winning percentage, what follows is a rundown of each rotation, using my best guesses as to who each manager will call upon in which spot, with the occasional alternative thrown into the discussion. Note that I've used full season stats for pitchers with more than one team.

Rangers:Yu Darvish (3.50 FIP), Matt Harrison (3.91), Ryan Dempster (3.60), Derek Holland (4.68), bullpen (3.61). Pythagorean estimate: .600.

Not only do the AL West-leading Rangers have the highest chance of reaching the postseason (98.8 percent, including a 96.1 percent chance of winning the division), but they also project to have the highest winning percentage once they get there even given a rotation without a true ace. Darvish has actually been touched for a 4.29 ERA, while Harrison has outperformed his peripherals en route to a 3.37 mark, but the difference basically comes out in the wash. Where things get trickier is identifying the fourth starter; with the loss of Colby Lewis for the season, manager Ron Washington is left with Holland, Scott Feldman and Roy Oswalt, the latter two of whom have higher ERAs than Holland thanks to subpar defensive support, not to mention considerably less stamina on a per-start basis. Swap out Holland for Feldman (3.72 FIP, but a 4.79 ERA) and their percentage rises to .610.

Yankees:CC Sabathia (3.31), Andy Pettitte (3.36), Hiroki Kuroda (3.83), Phil Hughes (4.74), bullpen (3.29). Pythagorean estimate: .598.

The Yankees have been struggling of late, in part because their rotation is in disarray; they're now tied atop the AL East, which they once led by 10 games. Pettitte is currently working his way back from a broken fibula suffered on a comebacker in late June; he threw 15 pitches to hitters on Wednesday and is aiming for a mid-September return. Ivan Nova (4.50 FIP) is on the DL due to an inflamed rotator cuff; he threw with no discomfort on Tuesday and could return mid-month as well. With a 4.92 ERA, Nova has been considerably more erratic than Hughes (who has a 4.18 ERA, with his 1.8 homers per nine biting him much less than expected), so it's difficult to see manager Joe Girardi tabbing the former over the latter. If Pettitte suffers another setback and Nova is swapped in, with the other starters moving forward, their Pythagorean percentage drops to .571, a significant hit.

Tigers:Justin Verlander (2.91), Max Scherzer (3.41), Doug Fister (3.37), Rick Porcello (3.66), bullpen (3.7). Pythagorean estimate: .584.

The Tigers are on the outside looking in right now, 3 1/2 games back in the wild-card race as well as a game back in the AL Central, but their rotation looks formidable thanks not only to defending Cy Young winner Verlander but also the surging Scherzer, who has allowed just four runs across his last five starts, and who has at least eight strikeouts in his last nine turns; overall, his 11.3 K/9 leads the league. Porcello, who strikes out just 5.4 per nine, is carrying a 4.58 ERA, nearly a full run higher than his FIP, thanks largely to a searing .351 batting average on balls in play at the hands of the Tigers' shoddy defense, which ranks dead last in the AL with a .675 Defensive Efficiency. All else being equal, if he pitches only to the level of his ERA, that would knock 15 points off the team's Pythagorean percentage.

White Sox:Chris Sale (3.31), Jake Peavy (3.55), Francisco Liriano (4.16), Jose Quintana (4.11), bullpen (4.30). Pythagorean estimate: .575.

There's more uncertainty here than it appears at first glance. Sale has been Chicago's best pitcher, but he has just three quality starts out of his last eight, and his mounting innings total may be catching up with him, as his ERA has risen from 2.11 to 2.93 in that span. Quintana has been rocked for 12 runs in five innings across his last two starts, and Liriano has seen his control woes return; he has walked 11 in his last nine innings across two abbreviated starts. Not pictured here is Gavin Floyd (4.74), who skipped his last turn due to elbow soreness after two starts of less than three innings apiece; slotting him in knocks about eight points off the team's Pythagorean percentage.

Angels: Weaver (3.69), Wilson (3.88), Greinke (3.18), Haren (4.17), bullpen (4.10). Pythagorean estimate: .572.

The Angels still stack up well on paper, particularly with the elimination of Santana. Weaver generates such a high percentage of infield flies that he tends to outperform his FIP considerably, on the order of eight-tenths of a run in each of the past two seasons, though that's offset by Greinke underperforming by a similar margin. If Weaver's tendinitis turns out to be a longer-term issue, Jerome Williams (4.15) or Garrett Richards (4.55) make for much better options than Santana (5.59); the team's Pythagorean percentage would drop to .565 with Williams slotted in and Wilson bumped to the front. A bigger wild card is the struggling bullpen, whose second-half ERA stands at 5.17, with a 4.58 FIP; maintaining that level of performance would cost the team 18 points of winning percentage.

A's:Brett Anderson (3.54), Jarrod Parker (3.42), Tommy Milone (4.01), A.J. Griffin (3.34), bullpen (3.72). Pythagorean estimate: .537.

The A's have been dealing with injuries and attrition in their rotation all season; most notably, they got Anderson back from Tommy John surgery just after losing Bartolo Colon (3.78) to a 50-game suspension. Now it appears they've lost Brandon McCarthy (3.72) as well after he underwent surgery for a skull fracture suffered when he was hit by a line drive. Anderson has only three starts under his belt; instead of using this season's 2.00 FIP, I've swapped in his career mark for the purposes of the model.

Rays:David Price (3.16), James Shields (3.62), Matt Moore (3.76), Jeremy Hellickson (4.93), bullpen (3.24). Pythagorean estimate: .526.

Take this ranking with a grain of salt; the Rays have allowed a league-low 3.26 runs per game, with their rotation delivering a league-best 3.47 ERA as well. Hellickson, in particular, has far outdistanced his 4.59 FIP during his two-plus seasons in the majors, delivering a 3.18 ERA; this year, he's at 3.41. Swap that mark in and the team's Pythagorean percentage rises to .551; the Rays are still held back by an offense that's scoring just 4.20 runs per game, 11th in the league.

Orioles:Jason Hammel (3.19), Wei-Yin Chen (4.15), Joe Saunders (4.15), Zach Britton (3.92), bullpen (3.76). Pythagorean estimate:.512.

The upstart Orioles' rotation has been in flux all season, as Chen and Tommy Hunter are their only pitchers to make at least 20 starts. Saunders was just acquired from the Diamondbacks via trade, while Hammel just returned from an eight-week absence due to knee surgery on Thursday night, delivering five innings of six-strikeout, one-run ball against the Yankees. Manager Buck Showalter has other options at his disposal, including Chris Tillman (4.23) and Miguel Gonzalez (4.46), but with Tillman dealing with an inflamed ulnar nerve and Britton on a roll (three runs and 29 strikeouts in his last four starts totaling 28 2/3 innings), I've pieced together the most optimistic picture possible — and it's still at the bottom, in large part due to the team's 4.30 runs per game scored, which ranks ninth in the league.