A major reason former Alabama linebacker Reuben Foster slipped to No. 31 in the first round of last week's draft is a shoulder condition that worried teams and could jeopardize his rookie season with the San Francisco 49ers, per league sources.

Despite surgery on his right rotator cuff, Foster's right shoulder was worrisome enough that some teams did not consider drafting him.

"The surgery didn't take," said one well-placed source with knowledge of the injury.

Last week, USA Today Sports reported that Foster slipped in the draft because at least one team was concerned he would need additional shoulder surgery.

Another source predicted that Foster would not make it through his rookie season and that the linebacker's shoulder could give out on any hit. The 49ers' doctors, however, are comfortable with the condition of Foster's shoulder and hopeful it will hold up, though they understand there could be a risk, according to sources.

Reuben Foster's shoulder scared off many teams in the draft, but the 49ers were comfortable enough with it to draft the linebacker with the 31st overall pick. Stan Szeto/USA TODAY Sports

Foster was sent home early from the combine in February after he had an altercation with a hospital worker. Because Foster left the combine early, the NFL did not have its own medical report on him until just days before the draft. By the time teams received it, there were enough concerns with multiple teams that, at the very least, it contributed to Foster sliding down the board, according to league sources.

One team said this week that Foster's shoulder exam during his medical recheck in Indianapolis was the reason it could not draft the former Alabama standout.