The Buffalo Bills are in the midst of their OTAs, which run through June 4. They will then have mandatory minicamp from June 9-11 and will break after that until training camp in late July.Throughout all these practices, players will be fighting for a spot on the initial 53-man roster. While there aren't many spots open, these three undrafted free agents have the talent to potentially steal a spot.Theron Gaines, LBOakland's Theron Gaines looks for a signal from the sideline during the Patriots win over Shelbyville. | Tom Beckwith / For The DNJ / USA TODAY NETWORKLinebacker isn't the strongest position on the roster, which is why Bills On SI writer Alex Brasky recently identified Theron Gaines as a dark horse to make the roster this year. Gaines didn't play against elite talent at Tennessee Tech, but he dominated against the competition he faced.Gaines secured an overall defensive grade of 85.4 from PFF and was more than effective against the run (79.7) and in coverage (86.7) during his final collegiate season. Not only is he well-rounded, but he has the right size to play inside linebacker in Jim Leonhard's defense at 6-foot-1 and 237 pounds.Right now, Terrel Bernard and Dorian Williams are the starters with rookie Kaleb Elarms-Orr as the primary reserve. Other backups include Joe Andreesen, Keonta Jenkins, and Jimmy Ciarlo, which means Gaines could find his way onto the team if no veterans are added.Jackson Acker, FBWisconsin Badgers fullback Jackson Acker rushes with the ball for a touchdown against the LSU Tigers. | Matt Pendleton-Imagn ImagesBuffalo is among a handful of teams that still employ a fullback, but they lost Reggie Gilliam to the New England Patriots in free agency. During OTAs, the Bills have two players fighting to fill the vacancy Gilliam left. Veteran free agent addition Ben VanSumeren, a former linebacker who turned fullback, and rookie Jackson Acker.Alex Brasky named VanSumeren a dark horse to make the roster this year, but Acker is someone to keep an eye on. The 6-foot-1, 247-pounder excelled as a pass blocker throughout his career, earning a PFF grade of 69.3 in this area during his senior season. He also provided a spark as a receiver, which would give Buffalo's offense another wrinkle.Earlier this month, we wrote about Acker's chances to stand out once the pads come on.Desmond Reid, RBPittsburgh Panthers running back Desmond Reid runs against the Louisville Cardinals. | Jamie Rhodes-Imagn ImagesRunning back is a pretty crowded position in Buffalo with James Cook standing out as the featured back. Behind him, Ray Davis and Ty Johnson have each played their roles well, with Johnson serving as an excellent option as a receiver out of the backfield. Davis and Johnson are also both contributors on special teams, with Davis averaging 30.4 yards per kick return in 2025.That said, Desmond Reid is still someone to keep an eye on. Reid is undersized at 5-foot-6 and 174 pounds, but fills multiple roles. He was a running back, slot receiver, and punt returner during his career with Pittsburgh. That versatility could help him carve out a role in the NFL, perhaps as early as this season if he gets up to speed quickly.Add us as a preferred source on GoogleFollow