Sean Lee replacement options are few and far between for Dallas Cowboys

Could Jonathan Vilma be the one to replace injured Dallas linebacker Sean Lee? (Scott Iskowitz/AP) Sean Lee may be the most irreplaceable part of the Dallas

Could Jonathan Vilma be the one to replace injured Dallas linebacker Sean Lee? (Scott Iskowitz/AP)

Sean Lee may be the most irreplaceable part of the Dallas defense, so his ACL injury Tuesday during the team's first OTA session threatens to leave the Cowboys reeling for months to come. Lee is reportedly expected to miss the 2014 season.

Free agency has dried up for the most part and the 2014 draft is in the rear view mirror, leaving Dallas with limited replacement options should Lee be sidelined into the regular season. More players will be available far deeper into the summer once roster cutdowns come into effect.

In the meantime, here is a quick glance at which players may comprise Dallas' Plan B:

• Jonathan Vilma: ESPN's Adam Schefter reported Tuesday that Vilma is "healthy and ready" after missing all but part of one game last season because of a knee ailment. Whether that clean bill of health is legit or not, Vilma clearly brings a rather substantial injury risk of his own with him. The 32-year-old ex-Saint has not played a full season since 2010.

Vilma spent several seasons as a 4-3 MLB before his role began to change and before Rob Ryan arrived with a 3-4 defense. Because of how worried the league is about Vilma's lingering knee issues, he might come cheap ... and he definitely brings more experience to the table than Dallas' in-house prospects.

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• Pat Angerer: Could this be the best option out there? It all depends on how quickly Angerer gets back to 100 percent following microfracture surgery. (Yes, another knee injury).

Angerer delivered 63 tackles and an interception over 11 games for the Colts last season, but he was miscast for their 3-4 attack. His best effort came in 2011, when he slid into a starting role at middle linebacker in what was then a 4-3 look for Indianapolis. Angerer's tackle total that season: 148. When he's healthy, Angerer can track the football with aggressiveness from the middle of the field.

• Dan Connor: Connor was too early to the Dallas party in 2012, showing up one year before the team transitioned from a 3-4 defense to a 4-3. By his own admission, the latter better suits his abilities.

"I'm more of a 4-3 guy than a 3-4, which I was in last year, so I wanted to get back into that 4-3," Connor said after signing with the Giants before the 2013 season. "I’m just more comfortable playing it."

He never had much of a chance to show off his talents in New York, despite being signed as a prospective starter. Connor landed on I.R. with a neck injury following just one game, then was released in November. He finished out the year in Carolina where his career began.

• Kelvin Sheppard: Purely spitballing ideas here, but a quick glance through the NFL's depth charts reveal minimal middle linebackers available for the Cowboys — especially if Jerry Jones wants to avoid paying a premium (Dallas also does not have the cap space to take on a hefty contract).

Sheppard arrived in Indianapolis last season as part of a trade that shipped Jerry Huges to Buffalo. Sheppard was mediocre at best in the Colts' 3-4 scheme, after disappointing the Bills for two seasons after being a 2011 third-round pick. If he is to make anything out of his NFL career, odds are it will happen as a downhill thumper in a 4-3 defense.

Dallas could provide at least the opportunity to compete for playing time. It may not cost Jones much more than a conditional late-round pick, given that Sheppard may be fighting for his Indianapolis roster spot behind Jerrell Freeman, D'Qwell Jackson and others.

• Anthony Hitchens/Devonte Holloman: These are who the Cowboys currently have on the roster as possible Lee replacements, though 2013 signing Orie Lemon technically provides a third option. Neither Hitchens nor Holloman would make Dallas feel anywhere close to comfortable about its MLB situation.

Hitchens was a tackling dynamo at Iowa, leading the Hawkeyes with 124 tackles in 2012 and another 112 last season. A lot of that production came off the weak side, which is where the 6-foot, 240-pounder appeared ticketed for in the NFL. The Cowboys, however, dropped him in as a middle linebacker in rookie mini-camp — planning on Hitchens providing depth behind Lee during the season. They may not have the luxury to wait before finding out what he can do.

Holloman gave the Cowboys some minutes last season when the linebacking corps was thinned out by injuries. Could he survive in the middle? Maybe. There were rumors earlier this offseason that Dallas was toying with slotting in Holloman as its starting MLB and moving Lee out to the weak side. Team vice president Stephen Jones dismissed that idea in an interview with 105.3 FM: "We’ve discussed a lot of things and that’s not one of them. ... [Lee's] so good in the middle there and leading the way, leading the defense. It’s a natural spot for him to work from."