"It was an unfortunate thing, anytime a player like Thomas, a young talent, gets hurt," coach Marvin Lewis said. "You have to move on. It's a freak thing that happens."
Howard, a seven-year veteran from UTEP, was Cincinnati's leading tackler last season with 120 stops, and started in the Bengals' Week 1 loss to the Ravens on Monday night. He had four tackles, including a sack, and a pass defensed in the 44-13 defeat.
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To take his place on the roster, Cincinnati signed linebacker Roddrick Muckelroy. A third-year player from Texas, Muckelroy started three preseason games for the Bengals this summer, posting 17 tackles, including a sack. He was a fourth-round draft choice in 2010 by Cincinnati.
The Bengals (0-1) take on the Browns (0-1) on Sunday.
"We were lucky to get Muckelroy back here this morning," Lewis said, "and get going from there."
Muckelroy, who was one of the final cuts by the Bengals two weeks ago, was still in the area. He was scheduled to move back to Houston today before he received a call from the team last night.
Howard was signed by the Bengals last year following the lockout and took over at weakside linebacker when Keith Rivers had an offseason injury. Howard started 15 games and had four passes defensed and two forced fumbles. He led team in tackles in four of final six games last regular season, as well as the playoff loss to Houston.
With Howard out, Vincent Rey and Dan Skuta will see action against Cleveland. Rey has seen time mostly on special teams while Skuta has started four games over the past three seasons, including three at middle linebacker last year when Rey Maualuga had an ankle injury.
"It's unfortunate timing. Thomas is young enough, he might just have to take a hiccup for a second and move forward," Lewis said. "He's a wonderful, wonderful human being and person. He understands things happen for a reason and he'll come out of this well."