The Buffalo Bills might begin their 2015 season without running back LeSean McCoy who suffered a hamstring injury during one of the team's practices last month. 

According to Josina Anderson of ESPN, a source said the magnetic resonance imaging (MRI) revealed a small tear in a part which was surrounded by stronger muscles in the glutes which was a good thing. 

Bills head coach Rex Ryan seemed positive late last month that McCoy would be joining them in Week 1, but he did not discuss any information regarding the running back's MRI. 

However, ESPN reported that earlier this week, Ryan is uncertain if McCoy can play in their opener, saying that if he cannot they would be relying on the "next man."

ESPN's source said, "It's way too early to say whether [McCoy] will play or not. He is doing a little bit more every day. But hell yes, I'm concerned about that."

"I can't say for sure he's going to be with us Week 1. I can't say that at all," the source added, also saying that it will take them time to get McCoy game ready and he will not be in shape once they play in Week 1. 

The source also said they are hoping McCoy will be ready but suggested that if he is not at a hundred percent, they should not be playing him to prevent aggravating the injury since they need him for the season. 

Buffalo finished this year's preseason at 2–2 with wins over the Cleveland Browns and Pittsburgh Steelers and losses suffered to the Carolina Panthers and Detroit Lions. 

The Bills will open the regular season on Sept. 13 hosting the Indianapolis Colts at the Ralph Wilson Stadium.

Last season, the Bills again failed to reach the playoffs for the 15th consecutive season after finishing the regular season with a 9–7 record.