When the Patriots went to Richmond last week for joint practices with the Redskins, they left tight end Rob Gronkowski behind. The big fella had been a regular attendee at every prior training camp practice this summer.

On Sunday, the first day back on the field in Foxborough, Gronk was back with his teammates and suited up in full pads, although he remained limited in the kind of work he could do.

Afterward, Gronkowski spoke to the media, insisting he had "no setbacks" last week while he focused on his rehabilitation with team trainers. He continues to work his way back slowly from a right knee injury sustained against Cleveland last December.

"Just a little time off to let the knee heal a little bit more. You know, you can't always be grinding on it 24/7 off an injury. You have to let it heal," he explained. "I'm feeling better since the time off, so, it's going well. My body kind of needed it, my knee needed it, that rest, when they went to Virginia. It was good progress."

Gronkowski's training camp practices have consisted mostly of individual and position drills. He has yet to take part in 7-on-7 or 11-on-11, but often works with QB Tom Brady and cornerback Darrelle Revis on red zone route-running and pass catching.

"It's good just to have a defender out there, instead of running all my routes against air. To break off a guy right in front of you, just like it's a game," he continued. "Having Darrelle out there giving me a little contact, pushing me on my routes, it's making me a better player. It's basically more of a drill for me. He's definitely learning, too, but he's not going full-out.

"I'm going full-speed in the drills I'm doing, but they're just limiting the drills I can do. Most likely, when I'm cleared for contact, it will be full-go, too."

When that will be, however, remains a mystery. Gronkowski asserted that he and the team's medical staff have no timeline for his return to full practice activity. He would only say repeatedly that he's "getting better every day."

Absentee Mallett

For the first time this summer, the Patriots practiced with just two quarterbacks. Brady and rookie Jimmy Garoppolo had to handle extra passing duty because Ryan Mallett did not take part. He didn't even attend Sunday's afternoon session.

Head coach Bill Belichick was asked afterward for the reason for Mallett's absence.

"There're all different players in different physical situations," he responded, "so, I'm not going to get into all that. We'd be here all day."

Belichick's use of the word "physical" would seem to suggest, however, that Mallett is in fact dealing with some sort of injury, which may have been sustained at the end of the first half of the preseason opener at Washington. Mallett, who started the contest, did not return to the game after halftime.

Mallett wasn't the only player who didn't take part, but he still has a job with the team, unlike three rookies: running back Stephen Houston and tight ends Justin Jones and Asa Watson. They were released prior to practice. In their place, the team signed veteran tight ends Ben Hartsock and Steve Maneri, as well as rookie tight end Terrence Miller.

"We're looking for guys that are improving and kind of when they stop making improvement, then sometimes you feel like you've got to move on," said Belichick. "We signed three players that we feel like will be competitive, but we'll see." 

The head coach also issued a statement Sunday, remarking on the retirement of former Patriots safety Steve Gregory, who was released by New England during the offseason. After trying to resurrect his career with Kansas City, Gregory announced last week that he was leaving the game for good.

"Steve Gregory was a true professional and a pleasure to coach," read Belichick's statement. "He was one of the most well-liked and respected players because everything he did was the right way, with a great attitude and in the best interests of the team. On behalf of the New England Patriots, we thank Steve for his contributions on and off the field and wish him our very best in the future."

Nose to the grind stone

It seems the Patriots are reverting to their traditional 3-4 defensive front. After beginning camp in the 4-3, which they've run almost exclusively the past couple of seasons, New England started employing 3-4 looks against the Redskins in Washington last week.

When they have, second-year lineman Joe Vellano has seen plenty of action, both as a nose tackle and an end. Vellano made the 2013 Patriots as an undrafted rookie out of the University of Maryland.

"Year 2, you still have to bust your butt and work hard," he said after Sunday's practice. "I feel pretty good, knowing the majority of the [playbook] coming in. It's a real big camp for me. Definitely, knowing you went out there and did some things [last year] you can build on. Trying to increase my role and do everything I can do, play multiple positions."

The differences between playing defensive line in the 4-3 as opposed to the 3-4 may not seem significant to the untrained eye, but Vellano maintains otherwise. His experience at Maryland, where he said the Terrapins played both 4-3 and 3-4 defenses, is helping him become a more versatile pro.

"You know, you move two or three feet [where you line up at the line of scrimmage], it doesn't look like much, but it is a lot of different reads, [opponents] are on you quicker. Your footwork, your base [are different]. If you don't get the reps, you have to learn off the guys in the classroom and learn from the guys playing the position ahead of you. You have to get a lot of mental reps, and the [on-field] reps you do get, you have to know all the calls and the techniques. The more you know, and the more positions you know, it's just going to make you a better football player."

Stock Watch

Buy: Bryan Stork – A no-show since being injured in the fifth practice, the rookie center finally returned to practice, albeit in a rehab role. He was, however, sporting a practice jersey as he took part in some warm-up activities, including snapping to the QBs as they loosened up before practice.

Sell: Ryan Mallett – After a dismal performance in the preseason opener, Mallett was not on the field at all for Sunday's practice.

Play of the Day: During 11-on-11, rookie QB Jimmy Garoppolo had a pass tipped at the line of scrimmage. Rookie defensive lineman L.T. Tuipulotu came down with the unlikely INT and rambled down field, drawing loud cheers from his teammates.

Training camp resumes Monday with an afternoon session that's open to the public. Check patriots.com for the latest dates and times, as the practice schedule is always subject to last-minute change.