Terrell Davis is issuing a stern warning to Saquon Barkley ... saying if the injured running back returns too early from his ACL injury, it could have DIRE consequences.
The Hall of Famer explained it all to TMZ Sports ... with Davis telling us when he rushed back early from a knee injury following the 1999 season -- it cost him A LOT.
"For me, I tell players coming back from an injury is sometimes you have to protect yourself from yourself," Davis says. "And, what I mean by that is we're very competitive and we want to come back and beat the timeframe."
"So, if the doctor says it's a six-week or six-month recovery -- whatever it is -- our minds is, 'I'm coming back in half that time. I'm coming back in three weeks or three months.'"
Davis continued, "I remember coming back and I thought I was ready to play and I was really trying to get back on the field but I think long term it hurt me."
Davis says if he had just taken the extra time to ensure he was 100 percent, the ending of his career could have gone MUCH differently.
"I always tell players," Davis says, "'Listen, I understand you feel like you're ready to come back, make sure you're sure. Make sure that you're ready to come back because you can do more damage if you come back prematurely than if you wait.'"
Barkley tore up his knee back on Sept. 20, 2020 ... and he's been rehabbing and training like a mad man to get back on the field ASAP.
In fact, the 24-year-old just posted video of some of his workout sessions last month ... showing he's already jumping off his injured leg.
It's all a great indicator that Barkley should be ready for the Giants' season opener in September ... but Davis is making it clear, Saquon NEEDS to listen to his body fully before he straps on the pads again.
As for what Davis is up to in retirement ... he spoke with us about his company launching its new 9.5 pH Alkaline water -- and you gotta see how fired up he is about the latest venture!