FOXBOROUGH — The Patriots officially placed tight end Rob Gronkowski on injured reserve Monday, ending his fourth NFL season.
Gronkowski suffered a right knee injury at the tail end of a 21-yard reception in the third quarter against the Browns Sunday. After an MRI was taken on Gronkowski Monday morning, a league source confirmed to the Globe that Gronkowski had torn the anterior cruciate and medial collateral ligaments in the knee.
The news that the tight end wouldn't be available for the remainder of this season was difficult for Patriots players to deal with a day later, after they watched Gronkowski cut down by Cleveland's T.J. Ward.
"It's definitely tough," said Matthew Slater, who was on his knees near Gronkowski, praying for his teammate, while the tight end was being tended to on the field. "We can't sit here and try to pretend that it's something that's easy and that we just can roll though. It's tough.
"Obviously injuries are part of this game, unfortunately, but when you lose guys, and guys of this caliber, it makes it hard on the football team, so we're going to have to continue to show the mental toughness we've shown all year and try to respond. But it doesn't make it easy mentally and obviously it doesn't make it easy physically, because replacing a guy like that is very hard to do."
The 24-year-old Buffalo-area native now faces at least one reconstructive surgery, which will be the sixth operation he has undergone since Nov. 19, 2012, the day after breaking his left forearm late in a game against the Colts.
Gronkowski needed three more surgeries on the arm, and also underwent a microscopic lumbar discectomy on June 18.
In February 2012, after the Patriots played in Super Bowl XLVI, he needed surgery to repair torn ligaments in his left ankle suffered against the Ravens in the AFC Championship game.
As he rehabbed and worked his way back into playing shape, Gronkowski missed the first six games of this season. In seven games back, he had a tangible impact on the New England offense, with the unit showing improvement in several key areas, most notably red zone efficiency and points per game.
Quarterback Tom Brady's numbers also got better when he had his trusted big man on the field with him.
But the fact that the Patriots did play without Gronkowski at the start of the year doesn't make things easier now.
"No. No," said running back Shane Vereen. "To lose a teammate and a friend like Rob, it's horrible, but as a team, we have to bounce back and I think we know that his wishes are for us to bounce back as strong as we can.
"We've got to work. Guys have to step up. They're going to ask us to do different roles than we've done before, and that's expected and we're just going to have to step up and guys are going to have to make more plays and hopefully the offense will be able to keep going."
Having a healthy Vereen could make things easier this time without Gronkowski than they were in September and October; the third-down back broke his wrist in the season opener and missed eight games.
"Unfortunately we've had to take the field without him in the past and we've had to figure out ways to still be productive without him, and we're going to have to try to do that again," Slater said. "It's really unfortunate that we face the circumstances that we do, but injury is a terrible part of this game.
"But it's a reality of this game and we kind of have to push through it, and like I was saying last night, we have to play for those guys that are not out there with us. They put a lot into it, and we can't pack it in now, so we've got to go out and play for those guys."
Gronkowski is the fifth Patriots starter to be placed on injured reserve (Vereen was the short-term IR designee), joining Vince Wilfork, Jerod Mayo, Tommy Kelly, and Sebastian Vollmer.
Too many times Patriots players have had to repeat the "next man up" mantra the team lives by in situations like these, but Slater gave a refreshing response when asked about the pulse of the team after seeing yet another player suffer a significant injury.
"Look, we're not robots; we're not going to pretend like, 'well, the show must go on and it is what it is,' " Slater said. "We're hurting for Rob and it's going to be a tough loss for us.
"But that being said, we have a job to do and there's a lot left to be played for this season and we have to go out there and play, not only for Rob, but the other guys that we've lost this year, and realize that they put a lot into this and we owe it to them, and to ourselves to try and continue to push forward."
What's next for Gronkowski isn't exactly clear.
Dr. Bert Mandelbaum, an orthopedic surgeon at the Institute for Sports Sciences in Los Angeles and an expert in the treatment of ACL injuries, said doctors don't know exactly how damaged a player's knee is until going in for surgery.
"I think these injuries are ones of spectrum — there's different types of ACL injuries," said Mandelbaum, who is not treating Gronkowski. "The first is non-contact, with an isolation of the injury, around the ACL, with no meniscus or cartilage damage.
"And then there are contact injuries, like this one, with there's a torn ACL, torn some part of the MCL, and perhaps some other structures that they won't know until the time of surgery.
"I say there's a scale of 1 to 10, with 1 being the best, 10 being the worst, based on damage, instability, [and other factors]. That's something they'll learn once they go into surgery."
Gronkowski's MCL damage could determine when he has ACL surgery; in some cases, ACL reconstruction is delayed while the MCL heals, if it is stretched. If it is torn off the bone, a different course of action would be taken.
"Everyone wants to know what it is, when will he come back," Mandelbaum said. "But the prognosis and the time to return all depend on the injury, in terms of where it is on the spectrum."
Mandelbaum said athletes such as the Vikings' Adrian Peterson and soccer star David Beckham, who mended relatively quickly from their ACL surgeries, are "super healers." Beckham was back on the field in less than six months after suffering his tear in March 2010, and Peterson rushed for more than 2,000 yards less than a year after tearing his ACL.
They are not the norm, and Mandelbaum is wary of making comparisons.
A super healer with the right mental makeup and "a little bit of luck" can get back in six months, Mandelbaum said, but the standard time frame for professional athletes is anywhere from six to 12 months recovery.
"[Gronkowski] has been an amazing athlete and he's already come back from so much," Mandelbaum said. "He's a tough guy and it seems like he has that element to him, the 'mend it like Beckham' as I call it. He seems like a guy that will do the best he can under the circumstances."
Shalise Manza Young can be reached at email@example.com. Follow her on Twitter @shalisemyoung.