PITTSFORD, N.Y. (AP) Buffalo Bills running back LeSean McCoy hurt his left hamstring Tuesday night and is having tests to determine the extent of the injury.
Coach Rex Ryan said trainers informed him the hamstring is intact and has not been pulled off the bone, which he described as ''a real positive.'' The injury occurred about an hour into a joint practice with the Cleveland Browns.
Ryan didn't want to be pinned down on a timetable for how much time McCoy could miss.
''I really don't want to go there yet, because let's get the prelim reports,'' he said. ''Hopefully, this will be something that doesn't set him back too far.''
McCoy was running a route during a 7-on-7 red-zone drill when he suddenly pulled up short near the goal line. He slowly walked to the sideline holding the back of his left leg and then sat on the turf, where he was attended to by numerous trainers. He required help getting up, and didn't bend his left leg while slowly making his way to the locker room alongside team doctor Les Bisson and trainer Shone Gibson.
The injury could be a big blow for the Bills after they acquired the two-time All-Pro in a trade that sent linebacker Kiko Alonso to Philadelphia in March.
McCoy led the NFL with 1,607 yards rushing in 2013, and was regarded as the centerpiece in Buffalo's plan to establish a run-first offense under Ryan. The former New York Jets coach took over the Bills in January, replacing Doug Marrone, who stepped down on Dec. 31.
Buffalo is likely down to just two healthy running backs - undrafted rookies Bronson Hill and Ricky Seale - for its preseason game at Cleveland on Thursday night. Seale had just signed earlier in the day after Karlos Williams was taken to a hospital and had an undisclosed medical procedure on Monday.
Without discussing the nature of the procedure, Ryan said Williams will miss about two weeks.
''I hope they're quick learners,'' Ryan said, referring to Hill and Seale. ''We just picked up the kid from Stanford (Seale), and I said, `You're playing a half on Thursday.'''
Seale has suddenly gone from working with children who have autism in San Diego to preparing to get a significant amount of playing time at Cleveland. At least he is familiar with Bills coordinator Greg Roman, who coached Seale during his freshman year at Stanford.
Receiver Marcus Thigpen also has filled in at running back during practice.
The group was so depleted that Ryan had to cut short the offense's session against the Browns defense by about 20 minutes.
Veteran Fred Jackson has missed two weeks after hurting his hamstring. He is expected to resume practicing next week.
Boobie Dixon, another veteran backup, is expected to miss another two weeks after pulling a calf muscle. And Bryce Brown is out with an undisclosed injury.
''I've never seen it before,'' Jackson said. ''All I can say is we've got to go in and follow our treatments and hopefully we can get back by the season opener.''
The Bills offense also is down its top three receivers.
Sammy Watkins missed practice after experiencing tightness in his hamstring and pain in a gluteal muscle. Ryan said Robert Woods missed practice on Tuesday after experiencing tightness, without specifying. Percy Harvin is expected to miss at least a week with an undisclosed injury.
That left Ryan wondering what the makeup of his patchwork offense will resemble on Thursday.
''Probably as not good as we anticipate going into the season with,'' Ryan said. ''I don't know fellas.''
The injuries also could affect the Bills' three-way quarterback competition. Tyrod Taylor will start at Cleveland after Matt Cassel started in a 25-24 loss to Carolina last week. EJ Manuel is also in the mix, though Ryan hasn't determined if he'll get an opportunity to start this preseason.
''You evaluate based on what you see on tape,'' Ryan said. ''The next man's got to step up. And then the next man and the next man and the next man.''
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