O'Brien didn't want to go into details of Carter's injury out of respect for him and his mother, he said, but he did praise him for the work he put in this year.
"He's had an excellent season for us. Here's a guy, a young player, that came in here trying to learn a position that's very difficult to learn. Offensively, it's the second-hardest position to learn behind quarterback," O'Brien said.
"I thought, as a young player, he came in here and did a really nice job."
The 6-3, 247-pound Carter also left the Ohio State game on Oct. 27 with a foot/ankle injury and missed the following game against Purdue. After seeing some time against the Cornhuskers, catching one pass for 12 yards, Carter will have to look forward to 2013.
Matt Lehman and Jesse James will now see most of the snaps in the season's final two games, against Indiana and Wisconsin. Garry Gilliam is the other starter in O'Brien's two-tight end system.
O'Brien and the NFL?
It's reasonable to expect NFL teams to come calling for O'Brien after his first year as a collegiate boss is complete.
After all, he has weathered an unprecedented storm of sanctions in the wake of the Jerry Sandusky child sex-abuse scandal and has led the Nittany Lions to a respectable 6-4 (4-2 Big Ten) record, even though some key players transferred or left the team.
Asked about whether he's thought about how he'll handle job requests from NFL teams, O'Brien quickly deflected the question.
"I'm focused on Indiana; we're 6-4, trying to get that seventh win, and we just really want to do a great job coaching this team this week for the Indiana game," O'Brien said.
O'Brien, the former offensive coordinator of the New England Patriots, has let NFL scouts attend Wednesday practices this year to watch his players.
Jones to Robert Morris
On Monday, former Nittany Lions quarterback/tight end Paul Jones announced on Twitter that he will transfer to Robert Morris and play football there.
Jones, a redshirt sophomore from McKees Rocks, Pa., came to Penn State as a four-star quarterback recruit out of Sto-Rox High School, but developed some academic problems and missed the 2011 season. When O'Brien switched him from quarterback to a tight end a few games into this season, Jones was hesitant at first, then accepted the move, but left the team at the end of September.
Jones thanked Penn State when he announced his decision on Twitter.
"Just want to say thanks for all the great coaches that I learned from at [Penn State] past and present," Jones tweeted from @C1nd3rellaMan. Then, "Blessed for all the lessons I've learned and people I've met during my time at Penn State."