UNIVERSITY CENTER, Mich. (AP) _ Concerned about the recovery from knee troubles of starting tight end David Sloan, the Detroit Lions on Tuesday signed veteran tight end Keith Jennings.

In seven years with the Chicago Bears and one with the Dallas Cowboys, Jennings caught 107 passes for 1,082 yards and 10 touchdowns.

``We're going to take a very close look at him and see, and just let everything shuffle out at that position,'' Lions coach Bobby Ross said. ``We just don't know how that's going to end up right now.''

The Lions waived rookie free agent tight end Jon Blackman, who had been out of practice for a week with a knee injury.

Sloan has struggled to make it all the way back from multiple knee surgeries that cut short two of his first three seasons. He was expected to return to practice Aug. 1, but an ultrasound last week revealed excess fluid on his right knee, pushing back his return indefinitely.

Ross admitted his concern for Sloan's readiness prompted the move.

Second-year tight end Pete Chryplewicz has been practicing with a sore foot for the past five or six days. The only other active tight ends in camp are free agent acquisitions Walter Rasby and Werner Hippler.

Jennings said he comes into camp in reasonable shape after spending the past few months working out with members of the Chicago Bulls staff. To help him get into football shape, though, he was immediately thrown into the mix in Tuesday afternoon's workout, without even an orientation session, or a working knowledge of the play book.

``I haven't even eaten breakfast yet,'' Jennings said. ``They called me last night, and I had to get up this morning at 4:30, catch a flight at 6, sign my contract, get a physical, pick up my pads and get out here for practice.''

Jennings had visited the Lions during each of the last three free agency periods, but was never offered a contract. His relationship with Ross went back a long way, however, and that helped cement the deal.

``I've known of Jennings for a long, long time, and I've always liked him,'' said Ross, who was coach at The Citadel in Charleston, S.C., when Jennings was a prep wide receiver at nearby Summerville High School. ``I know he has good hands, plus he's a fairly decent-sized guy who's a good blocker. He came in here today and did a couple of nice things.''

In the 11-on-11 passing drill, Jennings made a great diving grab.

``I don't know if I ran the right route or not. But even if I ran the wrong route, I've got to make the play because the ball's right to me, right?'' he said. ``That's how you make it in the NFL. You don't stick around the NFL if you're not making plays, and that's true everywhere you go.''