John Ross' NFL combine record is in serious trouble this week ... 'cause Alabama star receiver Henry Ruggs WILL run a 4.20 40-yard dash in Indy -- so says his Tide teammate.
"Somewhere around that range," Alabama cornerback Trevon Diggs tells TMZ Sports. "That kid's fast!"
Of course, Ross currently holds the mark for quickest 40 time ever at the NFL's marquee pre-draft event ... logging a 4.22 back in 2017.
But Ruggs has a legit shot of breaking that mark when receivers run this week ... because during his time at 'Bama -- he FLEW by defenders on a regular basis.
"Ruggs is real fast," Diggs tells us. "He's going to run a real, real, real good time."
As for how that pure speed will translate to the NFL ... Diggs says he has no doubts the guy will be a stud -- saying his skill level is right on par with Tide superstar Jerry Jeudy's.
"He got good routes, he's fast, he's a playmaker as well," Diggs says. "Like, you get the ball in his hands, like, no one is going to catch him. Like, nobody."
But when it comes to which receiver gave him the most trouble during his 'Bama days ... ya gotta hear Diggs' answer -- 'cause it just might surprise you!!