In the last few seasons, Pro Bowl linebacker Sean Lee has become the heartbeat of the Dallas Cowboys' defense.

However, it has often been riddled by the injury bug that has significantly limited his time on the field. That is once again the case as Ian Rapoport of NFL Network is reporting that Lee could miss the next couple of games.

The 31-year-old had to be pulled out in the first quarter of Sunday's 27-7 loss to the Atlanta Falcons due to a hamstring injury. If this continues to linger on, it could have a huge impact on the Cowboys defensively over the next three games over a 12-day stretch against the Philadelphia Eagles, Los Angeles Chargers, and Washington Redskins.

Sean Lee
Isaiah J. Downing/USA TODAY Sports

Lee had missed two games earlier this season because of a hamstring strain, which Dallas had lost both contests that he sat out. In fact, they have lost five consecutive games that he either did not play due to injury or was pulled off the field with precautionary measures in mind.

On top of that, in all three games that Lee did not play into the second half, the Cowboys have given up 27 or more points with opposing teams averaging 32.3 points in those contests. Meanwhile, Dallas has allowed only 18 points per game in the six other games where he was healthy.

They are also allowing opposing quarterback to hold a passer rating of 85.6 with Lee in the fold, which jumps to 107.8 when he is off the field. Things are far worse against the running game with teams averaging 3.5 per carry with him in the trenches and 5.5 per attempt without the two-time Pro Bowler.

The Cowboys will likely depend more heavily upon rookie Jaylon Smith to lead the linebacker corp while Lee is on the mend. Veteran linebacker Justin Durant is also expected to take up a much larger role in the meantime.