The Giants' general manager said at the NFL Combine that he doubted the wide receiver was playing with two torn hamstrings during last season.
Reese said that the team's medical staff would have caught anything so severe, and chalked Beckham Jr.'s assertion up to bravado.
"I don't know about that," Reese said of Beckham Jr.'s purported injuries. "I think he's trying to be a hero. I don't think you can play with two [tears in your] hamstring and run fast like that."
The Giants general manager added that Beckham Jr. would likely not have played in the Pro Bowl and in some of New York's games later in the season had he been dealing with an injury of that nature.
Beckham Jr. did deal with hamstring injuries during last season. According to the wide receiver, the first injury occurred prior to training camp. He was injured again before the team's preseason game against the New York Jets.
Beckham Jr. missed the entire preseason as well as the first four games of his rookie year due to hamstring problems. On Saturday, Reese said the team was responsible for rushing Beckham Jr.'s recovery, and caused him to miss the first quarter of the regular season.
However, Reese was confident that the 22-year-old's injuries did not worsen so dramatically once he returned.
"According to our doctors, it was healed up," Reese said. "He may have gotten fatigued later in the season, but yeah, I don't think you can go out and run like that if you have [tears in your hamstring]."
Beckham Jr. said in January he aims to be fully recovered by the beginning of training camp this year, and plans to play at full strength next season.
The NFL Offensive Rookie of the Year winner had 91 receptions for 1,305 yards and 12 touchdowns. The Giants finished the season 6-10 and in third place in the NFC East.
- Christopher Woody