Back injury keeps Rob Gronkowski out of Patriots practice

Patriots tight end Rob Gronkowski was at practice Wednesday, but missed Thursday’s session.Stephan Savoia/AP

FOXBOROUGH — The Patriots’ off week and the rest that came with it was not enough for the team’s star tight end.

Rob Gronkowski missed his second practice in three days on Thursday, and this time it was not just because of the knee injury that has plagued him since the end of November. The Patriots — after initially releasing a practice report that cited just the knee issue — amended the report to include Gronkowski’s back as reason for his absence, throwing a significant kink into the they’ll-be-fine-if-they’re-healthy line of thinking that has followed the team in recent weeks.

A league source indicated the back problem was also the reason Gronkowski missed practice on Tuesday. The team was not required to release an injury report that day.

The injury update Thursday came shortly after a report from ESPN that Gronkowski spent part of his day in a Boston hospital receiving treatment on his knee, including an injection. Ian Rapoport of the NFL Network later reported that Gronkowski did not receive a knee injection, but did receive treatment.

Asked prior to practice Thursday about Gronkowski’s status, coach Bill Belichick said, “We’ll list the players after practice like we do every day.”

Gronkowski did not speak with the media Thursday and was not spotted during reporters’ 45-minute access period in the locker room.

This is the latest in a series of back-related issues for Gronkowski. In 2009, the summer before his final collegiate season, he suffered a ruptured disk and nerve damage that required surgery. He didn’t play that year, then entered the 2010 NFL Draft.

Gronkowski’s second back surgery came in June 2013 to repair a herniated disk. He didn’t play until mid-October that year, while also dealing with other health issues.

Now, with the Patriots set to host the Chiefs in a divisional-round playoff game Saturday, Gronkowski’s back is acting up again.

The knee injury has troubled Gronkowski since a low hit Nov. 29 against the Broncos. He missed one game but hadn’t been on the injury report since Week 15. He declared that week that he was back in a normal routine.

In his four games since then, Gronkowski has averaged 3.8 catches and 61.3 receiving yards. Before the injury, he averaged 5.2 catches and 84.6 receiving yards.

Linebacker Jonathan Freeny and guard Tre’ Jackson also missed practice Thursday.

Among those listed as limited on the injury report was a trio of key players expected to return for Saturday’s game: receiver Julian Edelman (foot), linebacker Dont’a Hightower (knee), and tackle Sebastian Vollmer (ankle).

Prior to practice, Belichick explained that the status of injured players is fluid up until game time.

“A lot of times when you have an injury, a player feels good enough to play and he is good enough to play,” Belichick said. “But it’s a 60-minute game, and there are a lot of snaps and a lot of hits out there, and as the game goes on, maybe that — whatever that happens to be — wears down or fatigues.

“He’s healthy, but after a period of time he’s not able to sustain, doesn’t have the stamina with that particular body part or whatever the thing is, so it could change.”

Jackson was listed with a knee ailment, and Freeny was listed as “hand/not injury-related.”

The other limited players were the same as the day before: Danny Amendola (knee), Scott Chandler (knee), Justin Coleman (concussion), Nate Ebner (hand), Chandler Jones (abdomen/toe), Rob Ninkovich (shin), and LaAdrian Waddle (shoulder).

Familiar turf

The Patriots’ penultimate practice before Saturday’s game was different from all the others this season: They worked on the turf inside Gillette Stadium, as opposed to the grass practice fields out back. The team hasn’t played at home since a Dec. 20 win against the Titans.

“It’s as close as we can get to game conditions,” said Belichick. “Can’t get any closer than that.”

Several Patriots said it helps them generally get reacclimated to that environment after a nearly monthlong layoff between home games.

Kicker Stephen Gostkowski and punter/holder Ryan Allen go out there regularly, according to Allen, mostly to work on their footing. For everyone else, it’s helpful to get reps with the wind, lighting, and depth perception.

The Patriots also blasted music into the stadium to simulate game-like loudness.

“All the different things that can show up on game day, you get it really right there, instead of being on the practice field,” safety Devin McCourty said. “It’s really good for guys who haven’t played some of the crazy weather games that we get in this stadium. You never know what we can get Saturday, and being out there definitely helps.”

Unknown quantity

The uncertainty surrounding Chiefs receiver Jeremy Maclin — he has a high ankle sprain and is a game-day decision — could thrust rookie Chris Conley into a more prominent role in the Kansas City offense.

That, in turn, could be a little tricky for the Patriots defense. Conley, a third-round pick last spring, played in all 16 regular-season games, but was targeted only 31 times. He caught 17 passes for 199 yards.

When there’s not a significant quantity of film to review on Conley, the Patriots take what they can get.

“There are always players on the roster, particularly at this time of year, that maybe haven’t played a lot during the regular season but they’re one play away from playing,” Belichick said.

“You have to be ready for those guys, and we prepare for everybody on the active roster.

“It’s really a common thing every week. It’s just a different subset of players, but we always have to be ready for those guys, including the practice squad.”

Different worlds

McCourty provided a reminder of just how fortunate — and successful — the Patriots have been.

New England has been to the playoffs in all six of McCourty’s pro seasons, advancing to the AFC title game in each of the last four.

McCourty’s twin brother, Titans cornerback Jason McCourty, has never made it to the postseason. Tennessee has finished above .500 once in Jason’s seven seasons.

“He talks to me about it all the time,” Devin said. “That always gives perspective [on] preparing and being ready to go and trying to earn the right to come back here and prepare and get ready to go for next week. We have to go out there and earn it Saturday.”