Offensive lineman Damion Cook is out for the season due to a torn triceps muscle. The injury happened on the very first day of practice, but Cook simply taped it up and dealt with it. It recently became apparent that it was a more serious injury, however, as Cook will be headed to Alabama to have surgery done by Dr. James Andrews next week. The Lions placed him on the injured reserve today, ending his season.
Losing Cook is definitely a blow to the offensive line. He is a versatile player that was likely going to be in the competition for starting at left guard. Even if he didn't become a starter, Cook would have been a backup at multiple positions, which is always a plus for coaches when they have to make the active roster on game days. The more positions an offensive lineman can play, the better as it relates to depth for games.
To replace Cook's spot on the roster, the Lions signed wide receiver Bobby Sippio, who was with the Chiefs the previous two years. Sippio has played in the Arena Football League for the majority of his career, but in 2007 he ended up on the Chiefs' roster. He originally was on the practice squad, but an injury opened up a spot for him early in the season. In 2008, Sippio was released in the final round of cuts by the Chiefs. Earlier this year he signed with a Continental Indoor Football League Team since the AFL had halted operations (it looks like that move could be permanent).
An unknown player like Sippio who signs after training camp has already started doesn't have a great chance of making the team, but you never know with the wide receiver position. If Sippio comes in and shows he can catch the ball on a consistent basis, I would not be shocked if he got himself in the competition for a roster spot. After all, it's not like he's never been on an NFL team before, and stranger things have happened.