Patriots fear DE Derek Rivers lost for season with torn ACL, sprained LCL

Pats' Rivers suffers probable season-ending injury (2:24)

After Rob Ninkovich's retirement and rookie Derek Rivers' torn ACL and sprained LCL, Mike Reiss explains just how thin the Patriots are at defensive end. (2:24)

FOXBOROUGH, Mass. -- The New England Patriots fear they have lost Derek Rivers for the season after the rookie defensive end suffered a torn ACL and sprained LCL, sources told ESPN on Friday.

Rivers, who was New England's top pick in the 2017 NFL draft as a third-round choice out of Youngstown State, returned to Boston on Thursday and had an MRI. He will get a second opinion to determine whether surgery is necessary.

NFL.com first reported the results of Rivers' MRI.

Rivers went down on a kickoff coverage drill Wednesday in a joint practice with the Houston Texans at The Greenbrier in White Sulphur Springs, West Virginia. Head athletic trainer Jim Whalen examined Rivers' left knee on the field.

The Patriots traveled to Houston for Saturday's preseason game.

Rivers, who was selected 83rd overall, was projected to be part of a rotation at defensive end, which was arguably the Patriots' thinnest position entering training camp.

Trey Flowers, who led the Patriots with seven sacks last season, tops the depth chart at the position. After Flowers, there is a notable drop, which will likely lead the team to explore a free-agent signing or trade. Another option could be to try to entice Rob Ninkovich out of retirement.