On a team desperate for help at running back, with Jahvid Best out for at least the first six games because of concussion-related concerns, Leshoure will be counted on when he returns.
"We're going to need him," Schwartz said.
The Lions' second-round draft pick last year didn't play as a rookie because he tore his left Achilles tendon early in training camp. He was slowed by an injured right hamstring earlier this month, but flashed some potential against the Bills with agile moves after making a catch and power on a run.
"He made a guy miss on the edge," Schwartz said. "His best play was the touchdown run. He had a cutback available to him, but he smelled the goal line and put his head down and scored."
"We didn't have a perfect scenario on defense to start the game," Schwartz said. "We did a poor job on defense in that first drive."
The Bills then gave Tyler Thigpen an extended opportunity -- in part because Brad Smith had a groin injury -- to keep his job as their No. 2 QB, and he didn't take advantage of it. Thigpen had an interception returned for a touchdown in his second straight game and ended the team's comeback chances with another interception in the final minute.
Thigpen was 18-of-30 passing for 186 yards with a TD and two interceptions that contributed toward a 61.3 passer rating.
"I thought Tyler played good," Bills coach Chan Gailey said. "Everything was on the line for him, and he made the decisions tough for us."
"As the game was going on, I was trying to let him know how everything fit into our game plan and how all the formations and sets worked," Fitzpatrick said. "He's in a tough situation."
Buffalo got the ball back late in the game, trailing by six points, and chose to put Thigpen back in. He threw an interception to Justin Miller at the Detroit 14.
Detroit went ahead 31-24 early in the fourth quarter on Jason Hanson's 39-yard field goal after he had an attempt blocked and missed another.
Detroit stopped the scoring run on the ensuing possession when recently acquired cornerback Kevin Barnes broke up a pass on third down and Buffalo punted.
Copyright 2012 by The Associated Press