The Vikings are looking at an interesting decision at right guard as starter Anthony Herrera seeks a second medical opinion on the anterior cruciate ligament in his left knee that he re-injured in Sunday's 33-27 loss to the Packers.

If center John Sullivan returns this week from a concussion, as expected, the choices to start at right guard would be seven-year veteran Joe Berger and sixth-round pick Brandon Fusco. Berger's 21 NFL starts have all come at center; Fusco is a former Division II college player who never had played right guard in his life until Herrera was injured in the second half Sunday.

Coach Leslie Frazier said the team will know more Tuesday about Herrera's injury. But it's not looking good. The initial examination showed damage to the same ACL that was torn last season, causing him to miss the final six games.

Berger -- signed in Week 2 to give the team a bigger, more experienced interior backup at center and guard -- seemed to be a logical candidate to start at right guard if he's not needed at center again. But coaches appear to be leaning toward Fusco, who made no glaring errors in his NFL debut while the team was posting a season-high 435 yards of total offense.

For Fusco, Sunday's debut against the Super Bowl champions was surreal, to say the least, after four years at Slippery Rock.

"No offense to Slippery Rock," Fusco said. "It's a great school, but this is something else. ... I haven't been in an environment like this ever."

Fusco played left guard in high school. He went to Slippery Rock as a tackle, but was moved to center. "Never got a sniff at guard," he said. "So this has been different. But I'm getting used to it."

McNabb defends work ethicCalling it "ridiculous," Donovan McNabb responded to former NFL executive Michael Lombardi's NFL.com report that the quarterback was benched because he lacked the work ethic and commitment to the Vikings.

Lombardi wrote, "McNabb is at a point in his career that he does not seem to want to put in the time, is willing to show up late for meetings and practice, and expects to just play well."

Said McNabb: "I'm in here, one of the first guys in the building and the last to leave. For any of that to come out is ridiculous. I think the way I've gone about it, I would ask you guys obviously to talk to [offensive coordinator] Bill [Musgrave], talk to [quarterbacks coach] Craig Johnson, talk to Leslie.

"They'll tell you I haven't missed a practice. I haven't missed a meeting. ... You know, it's just another challenge throughout my career of, you hear sources. I would challenge those sources to come out and make it public because it's definitely not true."

Harvin has MRI on ribsReceiver Percy Harvin, who missed the second half of Sunday's game, was scheduled to get a magnetic resonance imaging exam on his ribs Monday.

"The ribs were really bothering him before the half," Frazier said. "He tried to play a few plays right before the half more like a decoy and by halftime it was just too painful."

Frazier said he expects safety Jamarca Sanford (concussion) to return this week. Cornerback Antoine Winfield (neck) remains day-to-day after missing the past three games.

Punt revisitedFrazier said he would still punt when he did in the fourth quarter Sunday. The Vikings had fourth-and-10 at their 36-yard line and trailed 33-27 with 2 minutes, 37 seconds to play. They had all three timeouts and the two-minute warning left, but never got the ball back because James Starks ran six consecutive times for 55 yards and three first downs.

Asked if he regretted giving the ball back to the Packers, Frazier said: "Not when I knew what the situation was with the clock, and the belief I had with our run defense and the timeouts we had and the two minute. I thought it was a perfect storm for us to get the ball back with plenty of time, and I thought we could get the ball back in better field position than where we punted. I fully believe it was the right thing to do at the time."