Six takeaways from the Patriots' Sunday practice

The New England Patriots were back on the field on Sunday for their fourth training camp practice.

There was more red zone work in this practice, but coach Bill Belichick did open things up a bit more, which seemed to help the offense.

The offense continues to struggle when the field shortens, but they showed a bit more life when there was more room to work in competitive drills.

Offensive guard Michael Onwenu, running back Ty Montgomery, offensive tackle Calvin Anderson and special-teamer Cody Davis were still absent from practice. Rookie center/guard Jake Andrews and wideout Kayshon Boutte were the newest additions to the list.

Here are six takeaways from Day 4 of Patriots training camp:

Conor McDermott gets first-team reps

Training camp opened with Riley Reiff being the Patriots’ top option at right tackle, but it might not end that way.

The veteran offensive lineman took a backseat for a second straight day to Conor McDermott. That does create some level of concern for a Patriots team that chose to pass on using one of its premium draft picks on a replacement for tackle Isaiah Wynn.

McDermott is a reliable backup and Calvin Anderson provides depth at the position. Reiff is 34 years old and is playing on a one-year deal with $4.15 million guaranteed.

Unless one of the veterans steps up or rookie fourth-round draft pick Sidy Sow hits his stride early, the right tackle position could once again be a trouble spot for the Patriots this season.

Jack Jones' stock on the rise

Jack Jones got in work playing on the top defensive unit on Sunday. It was a giant step in the right direction for Jones, who had been working with the second team throughout training camp.

The former Arizona State standout didn’t waste the opportunity, either.

He got in on a pass break-up against backup quarterback Bailey Zappe that could have been an interception. Jones has serious talent and potential as an outside cornerback. Assuming he’s able to stay on the field, he could make a formidable combination with rookie Christian Gonzalez while Jonathan Jones or Marcus Jones moves inside.

Jack Jones showed potential last season. So this is the year when he comes into his own and finally takes flight? Time will tell.

Is Michael Onwenu nearing a return?

Patriots starting guard Michael Onwenu, who is the best offensive lineman on the roster, was spotted doing conditioning work. He missed all of the spring practices while recovering from off-season ankle surgery.

It’s still unclear when he’s expected to make a return. The offensive line could use a boost with the way it's been bullied at times this summer, particularly in the red zone.

Not having Onwenu for an extended point was always going to be a problem for the Patriots. So the fact that he’s actually working out in some capacity and going through drills is a big positive.

Mac Jones gets hot in competitive team drills

Mac Jones was seeing the field well in 11-on-11s on Sunday. He was picking his targets methodically and taking what the defense gave him. If anything, it was a great example of what he’ll have to do this season to help give the offensive unit a fighting chance.

The Patriots lack a true No. 1 receiver on the roster. They don’t have that elite playmaker that can consistently separate and beat one-on-one coverage. So a lot of what they do will rely heavily on timing, precision and taking advantage of mismatches.

Jones will have to consistently fit passes in tight windows, while also being careful not to turn the ball over. It’s a tall order for a third-year quarterback dealing with his third straight offensive coordinator, but Jones has the talent to make it work.

Jalen Mills spoils Bailey Zappe's strong day

Sunday’s practice was easily one of the better practices for the Patriots’ quarterbacks. Bailey Zappe looked especially strong in the early sequences. But on his final rep, he was picked off by veteran safety Jalen Mills after attempting to force a throw to tight end Scotty Washington.

After practice, Mills talked about getting beat by the same play earlier in camp for a touchdown. That mistake prompted him to study the film and make the necessary adjustments for the next time he saw a play like that thrown at him.

He was obviously licking his chops when he saw it again from Zappe and company. That entire sequence shows how important mental work is when it comes to being prepared on the football field.

Mills remains locked in a heated battle with Adrian Phillips, Jabrill Peppers and Joshuah Bledsoe for the top safety spot opposite of Kyle Dugger.

Rookie Marte Mapu moves up to the first-team defense

Rookie third-round draft pick Marte Mapu is making a strong impression at training camp. That much was clear when he took the field with the first-team defense on Sunday. He still had on the red non-contact jersey, but he looked like he belonged with the starters.

One of the biggest questions since the draft is where Mapu would fit. He’s a rare hybrid playmaker with the versatility to play safety, linebacker or come off the edge.

During this practice, the Patriots had him at linebacker, which is an area clearly in need of an upgrade. Mapu has the sideline-to-sideline speed, coupled with the playmaking abilities against both the run and pass to make an impact right out of the gates.

This article originally appeared on The Providence Journal: Offensive line continues to be a position of concern for the Patriots