Cowboys' Sean Lee reportedly tore his ACL during OTA

The Cowboys gave Sean Lee a six-year extension prior to the 2013 season. (David Bergman/SI) UPDATE (Wednesday, 10:30 a.m. ET): According to multiple reports,

The Cowboys gave Sean Lee a six-year extension prior to the 2013 season. (David Bergman/SI)

UPDATE (Wednesday, 10:30 a.m. ET): According to multiple reports, Sean Lee suffered a torn ACL during OTAs on Tuesdays. He's likely to miss the 2014 season.

After just one full-team OTA workout — less than one OTA workout, actually — the Dallas Cowboys could be facing a crisis on defense. Sean Lee, the Cowboys' talented but fragile linebacker, had to be helped off the field with an apparent leg injury following a collision with rookie offensive lineman Zack Martin.

The NFL Network's Ian Rapoport tweeted: "Cowboys coach Jason Garrett talking to media, says they’ll evaluate Sean Lee’s left knee later. Players immediately feared it was serious."

According to ESPN's Calvin Watkins, Martin blocked Lee to the ground on a screen pass, leading to the injury. Lee has struggled to stay healthy in the past, missing 10 games in 2012 with a toe injury and five last season after hurting his neck. Lee also blew out his right ACL while at Penn State.

Making the whole situation even more difficult for the Cowboys: these early OTA practices are, by rule, of the non-contact variety. (Mike Fisher of 105.3 tweeted that Martin's block on Lee was "clean" and "Lee [was] slipping on the play.)

From Watkins, video of Lee limping off the field Tuesday:

"I really don’t know what happened there," Martin said, according to the Cowboys' website. "It was just a football play and we were both going full speed. I really don’t know."

The Cowboys already have enough question marks on defense without again having to worry about Lee's status. Dallas handed Lee, now 27, a six-year contract extension worth $42 million prior to the 2013 season. At the time, Lee was coming off a year in which he had played just five games. The Cowboys believed that Lee's 2012 season -- 105 tackles and 15 games -- was more indicative of what they would get from him on a regular basis.

Lee still finished the 2013 campaign with 99 tackles, including a combined 34 over a two-week span against San Diego and Denver. Time and again, Lee has proven himself to be one of the league's most talented young linebackers.

That is, when he's healthy. Though Dallas won three of five games sans Lee last season, the team's issues on defense are no doubt exacerbated when Lee is out of the lineup. The best MLB options on the depth chart behind Lee are 2014 fourth-round pick Anthony Hitchens and 2013 sixth-rounder Devonte Holloman, who saw action in nine games for Dallas as a rookie.

Regardless of how much time Lee misses on account of Tuesday's trouble, the Cowboys may be wise to toy with some alternate plans in their linebacking corps. Hitchens, Iowa's leading tackler in both 2012 and '13, may be able to handle middle linebacker duties on a short-term basis, but throwing him into the starting lineup is far from an ideal plan out of the gate.

Very few desirable options remain in free agency, should the Cowboys need to go that route: Jonathan Vilma, hobbled by his own knee issues, and longtime NFL vet Will Witherspoon may be the best of the bunch.

The only silver lining for Dallas here, if there is one, comes from the date: May 27 is 103 days from the team's season-opener against San Francisco. That gap leaves time for Lee to bounce back or for the Cowboys to figure out their next move.

In the event that Lee dodged major injury, the Cowboys may want to consider an approach with Lee similar to the one Detroit took with Louis Delmas last offseason, essentially shutting him down until the regular season began. This Dallas defense is far better with its captain on the field, so figuring out some way to keep him there will be priority No. 1.

[si-nfl-player id="87db806819d8447f8e7ff37efd459032"]