TAMPA — One costly fumble Sunday did what two seasons with the worst average per carry in the NFL couldn’t do: Put Doug Martin on the bench.Bucs coach Dirk Koetter had stuck with Martin, starting him Sunday even after Peyton Barber rushed for 102 yards last week. Martin, who missed last week’s game with a concussion, had only 26 yards on 10 carries in Sundayin a 24-21 loss to the Lions. His fumble on third down at the Detroit 23-yard line late in the second quarter put him on the bench the rest of the day."That tends to happen when you have an effective back like Peyton Barber," Martin said after the game. "He’s been effective. Last game, we saw what he could do. When you turn the ball over and you fumble, your chances get cut pretty short, so that’s what happened there."The Bucs committed five turnovers Sunday, a season high and matching their most in any game since 2011. Barber finished with 58 yards on 12 carries, including a 16-yard run to the 2-yard line to set up the tying touchdown with 8:05 remaining."It was tough sledding at first, but I feel like I get stronger as the game goes on," Barber said. "Doug did a great job. I just wound up being the guy in the second half."Martin is averaging 3.1 yards per carry, the worst among any NFL back with 100+ carries. Last year, he averaged 2.9 yards, also worst among any qualifying back."It was Peyton’s turn to start off in the second half," Koetter said. "He was doing a good job. We stayed with him. Then we used (Charles) Sims there a little bit in the last two drives."Given the ball with a tie game and 4:49 to play, Koetter opted for Sims at running back, and he had an 11-yard carry for a first down. But he was stopped for no gain on the following play, then dropped a screen pass on third-and-10, and the Lions won the game on the drive that followed.Barber said he understood Sims getting the nod late. The Bucs prefer his pass-catching ability in a two-minute drill setting."I know I have a role. Everybody has a role," Barber said. "It’s nice to play well, but at the end of the day, a loss is a loss. It would feel a whole lot better if we won."Martin is due to make $6.75 million next season, and the Bucs would have no cap ramifications from cutting him. Sims is an unrestricted free agent, so there’s the potential for major change in the Bucs’ backfield.Barber, who made the team as an undrafted rookie out of Auburn last season, had just 88 rushing yards in the team’s first 11 games, but has 160 in the last two. The most that Martin has had in back-to-back games in the last two seasons is 150, against the Chiefs and Seahawks last year.