Vikings still have concern at linebacker depth

Near the end of Thursday's practice, after a play near the sidelines, Vikings middle linebacker Erin Henderson came off the field in pain, then kicked a cooler.

The good news: It was not as serious as it appeared.

Henderson had his heel stepped on. After having the heel — which was bloodied — bandaged and the ankle taped, he returned to action briefly before leaving the field before practice ended.

"He just went in to let them take a look at his heel,'' coach Leslie Frazier said. "He should be fine."

Still, it pointed up how precarious the Vikings' depth is at linebacker, particularly in the middle. Second-year player Audie Cole replaced Henderson with the first-team defense.

Frazier said Cole has improved significantly in his second season. "We have more confidence in him today as a middle linebacker than we did a year ago," Frazier said. "I think he's going to be a capable guy should something happen to Erin.''

The Vikings, keeping with their intent to prepare for Sunday's preseason game in San Francisco as if it were a regular-season game, went so far as to have crowd noise played during some drills. The starters will play into the second half, the first drive will be scripted.

"We want a higher level of execution this week," Ponder said. "It's against a great opponent, it will be a great barometer for us as a team. We want high execution and a lot of plays."

Vikings rookie punter Jeff Locke had a strong performance in Buffalo after an up-and-down preseason debut. He had a 48.9 average and a 39.7 net — a figure hurt by a 34-yard return that special teams coordinator Mike Priefer said wasn't Locke's fault — in seven punts. Most impressive were the three punts Locke had downed inside the 20, including two inside the 5.

Locke has proved he has the leg for the big punts. But his situational punting is proving a plus, particularly the Aussie-syle kick he utilizes on a shorter field. The kick is designed to produce an end-over-end ball flight that, when done correctly, will often produce a backward bounce. That is particularly useful when trying to down punts deep in an opponent's territory. Nearly a third of NFL punters employ some variation of the kick. But Priefer said Locke is unique in that he gets the desired bounce while keeping a lot of hang time.

Locke learned the style in college from Aaron Perez, whom he followed at UCLA. But it took him a while to perfect it. "It took me two years to be able to do it," Locke said. "I couldn't get it to go downfield at all; it used to just go straight up in the air. In the summer before my junior year I finally figured it out.''

The result: He had 60 punts downed inside the 20 in his final two seasons with the Bruins.

• Defensive coordinator Alan Williams said cornerback Josh Robinson has done a good job moving inside to the slot in nickel situations. "[Robinson is] much more comfortable than I previously thought, because he had never been inside before," Williams said. "He's coming along faster than I think that he even thought he would.''

• Receiver Jarius Wright, who sustained a concussion in Buffalo, was on the field in pads Thursday but didn't take part in drills. Frazier said he has one more test to pass before returning to action and that Wright wouldn't play Sunday.