BEREA – Cleveland Browns running back Jamal Lewis will miss Sunday’s game with an unspecified head injury, raising the possibility that his NFL career is over.

Lewis was listed as out on Cleveland’s injury report, as was starting safety Brodney Pool, who sustained at least his fourth known concussion during Sunday’s loss in Cincinnati and is likely out for the season.

The 30-year-old Lewis, who last month said he intended to retire after this season, was not in the locker room during the session open to the media. There were no street clothes in his cubicle and a Browns spokesman did not give a reason for Lewis not practicing.

Browns coach Eric Mangini did not mention Lewis’ injury during his news conferences this week.

The team has not placed Lewis or Pool on injured reserve. Lewis’ agent, Mitch Frankel, did not immediately return phone messages seeking comment.

A punishing runner who has battered would-be tacklers since entering the league in 2000, Lewis has been bothered by assorted leg injuries all season. If he is placed on IR, it would bring an unceremonious ending to a brilliant career.

Lewis has rushed for 10,607 career yards, ranking him 21st on the NFL’s all-time list and just 36 yards behind Ricky Watters (10,643) for 20th place. Lewis was the league’s offensive player of the year in 2003, when he rushed for 2,066 yards with Baltimore.

Unfortunately, Lewis’ final season has been his worst. He has rushed for 500 yards on 143 carries – a 3.5 average – and has not scored a touchdown. He did not start in Sunday’s game at Cincinnati, but came in for the second offensive play and finished with a team-high 40 yards on 11 carries.

Lewis’ final carry was a 1-yard run with 14:02 left.

Earlier this season, Lewis, an offensive co-captain, criticized Mangini for working Cleveland’s players too hard in practice. He also questioned the team’s lack of an offensive identity. Lewis backtracked on his comments a few days later, blaming reporters for ‘blowing it out of proportion.’

Lewis seemed content with the idea of retirement, and said he was looking forward to life away from football. He owns several lucrative businesses, including a trucking company based in Atlanta.

Lewis signed as a free agent with the Browns in 2007. He rushed for 1,304 yards that season – the most by any Cleveland back other than Hall of Famer Jim Brown.

While Lewis’ career is in question, Pool is also facing a difficult decision on his future.

A five-year veteran, Pool suffered at least his fourth known concussion in the third quarter on Sunday. Mangini said Pool would not play this week against San Diego and indicated the 25-year-old Pool’s season is over.

‘It’s not looking very positive,’ Mangini said. ‘He’s definitely not going to play this weekend and there’s a chance he won’t be playing again this year.’

Mangini said no decisions have been made about Pool’s future beyond 2009.

‘We haven’t talked about the long term,’ he said. ‘That’s a discussion for a later time period. You never want to have a conversation about injuries with anybody, but unfortunately it’s something that is a reality and it’s never a fun conversation but they are always important.’

Pool has started 10 games this season and 49 since the Browns selected him in the second round of the 2005 draft out of Oklahoma. In Sunday’s 16-7 loss, Pool was injured early in the second half. He walked off the field, was escorted to the locker room and did not return to the sideline.

Pool’s situation has many of his teammates concerned about his health – and their own. With concussions a hot topic in the league, players are learning more about the dangers of head injuries and their lasting effects.

Browns linebacker David Bowens has seen a big change in the way teams are treating concussed players.

‘Early in my career, it was like, ‘OK, he’s got a concussion, can he count to three?’ Now it’s a big deal. You see how the older players, how it’s affected their lives post-career and it is a serious issue. I think the awareness level has definitely heightened because of it, and the teams are taking better precautions. Safety issues regarding helmets, that’s gone up. There’s a lot of steps being taken.’

Browns wide receiver Mike Furrey said he spoke on Tuesday to former teammate Kurt Warner, who missed Arizona’s game last week against Tennessee with post-concussion symptoms.

‘I don’t think anybody really has an understanding yet of the symptoms and why things are happening the way they’re happening,’ Furrey said. ‘There’s no answers.’

Furrey said it’s not uncommon for a player to lie to a team doctor to keep playing.

‘When you’re talking about a little headache throughout the week, you obviously feel like you’re still going to be able to play on Sunday,’ he said. ‘But nobody knows the extremities of those headaches or the difference of a light one or a heavy one or not having any other symptoms, being nauseated and sick throughout the week.’

‘As a competitor you want to keep playing, so obviously you probably would stretch the story just a little bit to get back on the field and it’s just the nature of any athlete that wants to play on Sundays.”