Of the things Mike Zimmer initially listed as issues following the Vikings’ 17-10 preseason-opening victory against the Buffalo Bills on Thursday night, several didn’t turn out to be as bad as the coach thought once he’d watched the film.

The one that matched Zimmer’s postgame diagnosis? The issues in press coverage.

Defenders were too quick to open their hips after jamming a receiver at the line of scrimmage, Zimmer said, and sometimes gave too much space when playing off receivers. On offense, several of the Vikings’ young wideouts struggled to shake press coverage.

The coach thinks he knows why.

“A lot of the guys that we have [had for several years] haven’t had an issue with it,” Zimmer said. “But it takes work. And then when you play against somebody that you haven’t really studied, you know, we had a half-day of [play] cards on it. They might release a little bit different, or they might bump you a little bit different than what we do.”

Zimmer is among the coaches who have lamented the NFL’s offseason rules, which shortened each team’s spring program in the 2011 collective bargaining agreement and prohibited defensive backs from pressing receivers until padded practices in training camp. That has left young players searching for the right way to handle physical play on the perimeter in the NFL, and contributed to an uneven performance Thursday night.

The Vikings won’t spend much time game planning for the Seattle Seahawks on Friday night. Rather, they’ll look to clean things up in exercises such as the one they used Saturday, when they devoted a sizable chunk of practice to press coverage.

“We’re pretty simple in what we do — it’s basically, ‘Cover your guy,’ ” Zimmer said. “We didn’t have many mental errors. We just didn’t cover very good.”

Waynes sits out; Rhodes leaves briefly

Cornerback Trae Waynes, who left Thursday’s game because of a shoulder injury in the first quarter, was one of three Vikings players who didn’t take part in any of Saturday’s practice. Cornerback Tre Roberson and fullback C.J. Ham also sat out.

The Vikings got Jerick McKinnon, left tackle Riley Reiff, wide receiver Laquon Treadwell, linebacker Kentrell Brothers and defensive end Brian Robison back on the practice field, but Reiff, Treadwell and Brothers did little in team drills.

The team also had a brief scare late in practice when cornerback Xavier Rhodes collided with safety Anthony Harris while contesting a pass over the middle. Rhodes appeared to be holding his left side after the collision but later returned for the final stretch of team drills.

Elflein played well

Rookie Pat Elflein had a low snap to Taylor Heinicke in the third quarter of Thursday’s game, but other than that Zimmer said he was happy with the way the third-round pick played at center in his debut.

“Elflein played very, very well,” Zimmer said. “He had one bad snap, but he played really well. He missed one guy when he took a poor angle.”

Wilson makes plays

Undrafted free-agent linebacker Eric Wilson led the Vikings with six combined tackles on defense, as well as one on special teams, and deflected two passes. He did it while playing out of position at middle linebacker, as the Vikings looked at Edmond Robinson, Emmanuel Lamur and Ben Gedeon at weak-side linebacker.

“He can run around out there,” Zimmer said.