The New England Patriots' already thin defensive end corps has taken another blow.

After injuring his knee during a kickoff drill in the team's Wednesday joint practice session with the Houston Texans this week, it appears rookie defensive end Derek Rivers has torn his ACL.

The Youngstown State product, who was New England's first pick in the 2017 draft (83 Overall), was sent back to Boston for further testing on Thursday.

That testing has reportedly led to a diagnosis of a torn ACL and sprained LCL. Rivers is still set to get a second opinion, to confirm whether or not he will need to undergo surgery.

The 23-year-old was not expected to play a key role on the 2017 team, though he was expected to plays in a rotation. While his loss might only initially hurt as a depth concern, it will likely hurt his progression next season.