Center Pat Elflein is not participating in spring practices, but the Vikings' second-year center said he's still on track to return for the start of training camp in late July.

Elflein said "everything's good" with his rehab schedule, which has held him out of drills during organized team activities (OTA's). He took part in the Vikings' annual charity golf tournament in Shakopee on Wednesday.

The former Ohio State star dealt with two injuries at the end of his rookie season. He declined Wednesday to discuss whether it's the fractured left ankle, suffered in the NFC Championship loss, or a shoulder injury he's still rehabbing. His shoulder was injured Dec. 3 in Atlanta, forcing him to miss two of the last six games.

The Vikings want Elflein to add strength to his 6-foot-3 frame, but he'll have some catching up to do because of the rehab.

"You'd like to be training the whole offseason," Elflein said. "But this is part of the game, just like putting on a helmet. This stuff happens. It'll knock you back a little bit. You just have to work twice as hard to come back on top."

Aside from getting back to "full strength," Elflein said he's hoping to also grow with the nuances in making protection calls at the line of scrimmage.

"Being able to see tendencies better," Elflein said. "Just kind of work on my mental game."

Treadwell's teamwork

Receiver Laquon Treadwell has seen plenty of work with the Vikings' top three-receiver set during OTAs this spring, and as he heads into 2018, he says he's got a better staff of people around him to help him improve.

He worked in Texas this offseason with personal trainer David Robinson, who coaches receivers such as Antonio Brown and helped Treadwell get ready for the 2016 draft. Treadwell, who had 20 catches last season after making one as a rookie, said he's working closer with a nutritionist, as well as massage and acupuncture specialists, to put himself in better shape.

"Coming in, typically I didn't have a trainer; I just worked hard and did different drills," Treadwell said. ''Going into Year 3, I have a better team round me. There's lots of different things I've done better and learned over the years I've been in the league."

Remmers remains at guard

Mike Remmers remained at right guard, where he finished last season, during OTAs this week. He's spent most of his time this spring at guard after signing a five-year, $30 million deal a year ago to be the Vikings right tackle.

The Vikings like Remmers' fit at guard with Rashod Hill, who might be the superior pass protector, protecting the edge at right tackle.

"Mike's a very instinctive player in there," coach Mike Zimmer said. "He sees a lot of things. He's got good quickness, good power."

Rookie tears ACL

Rookie Hercules Mata'afa had just started settling into the defensive line again when he tore his anterior cruciate ligament Wednesday during practice, according to a league source.

Mata'afa, the former Washington State star defensive tackle, signed with the Vikings as an undrafted free agent last month. The Vikings originally tried Mata'afa, listed at 6-foot-2 and 254 pounds, at linebacker. That experiment lasted only a couple of days, Mata'afa said recently, leading to his move to defensive end.

"With the big dogs," Mata'afa said Tuesday. "Feels like home."

Star Tribune writer Ben Goessling contributed to this report.