SAN FRANCISCO — Bryant Young considers this the most difficult season of his career and, following Sunday's loss, the 14-year veteran intimated that he'll retire when it's over.

"Let's be real about it: My days are numbered," Young said. "I'll just leave it at that. Read into it what you may."

Young, 35, considered retiring after last season but decided to come back, believing the team was on the brink of playoff contention.

"This has been one of the most emotionally tough and mentally tough years I've ever been through because of the expectations I had," Young said.

Young, who signed a one-year contract for 2007, is eligible for free agency. But he said last year that he had no desire to play elsewhere.

Young has started all 13 games this season and his 6.5 sacks lead the team. He's the last player remaining on the roster from the 49ers' 1995 Super Bowl winning team. He joined the club as a first-round pick out of Notre Dame.

TEAMWORK: Coach Mike Nolan called the defensive plays Sunday in consultation with defensive coordinator Greg Manusky, who missed much of the preparations leading up to the game after his father died.

Manusky was in Pennsylvania with his family when his father, Frank, 72, passed away Tuesday. He returned for a practice Thursday but then flew back to Wilkes-Barre to attend Saturday's funeral services.

"Greg and I collaborated on the calls," Nolan said. "Typically, I initiated most of them because I was here all week. But Greg and I were in constant communication and there were a few cases where I became the head coach again, and he made a few of the calls. It was a joint effort."

PAIN IN NECK: Left tackle Adam Snyder left the game late in the fourth quarter with a neck sprain, and Kwame Harris came on to play a couple of series in his place. It was the first time Harris had played left tackle in three years. Harris moved to right tackle in 2005 but lost his starting job to rookie Joe Staley in training camp.

Harris has been taking repetitions as the backup for both tackle positions since Jonas Jennings was lost to a season-ending ankle injury last month.

Also on the injury report was defensive tackle Ronald Fields (shoulder sprain) and linebacker Jeff Ulbrich (ankle).

NFL HISTORY: The Vikings' Kevin Williams and Pat Williams became the first pair of NFL defensive tackles to have interceptions in the same game for the same team.

Defensive end Spencer Johnson picked a fumble out of midair.

But it wasn't exactly an accident. Pat Willams said the Vikings work on snatching balls out of the air every Friday in practice. Coaches set up a line of defenders — "an assembly line," Williams called it — and throw passes for the players to intercept and roll fumbles for them to recover.

"That drill came in handy today," Williams said.

Kevin Williams' interception came on the first pass of the day. Trent Dilfer's pass smacked him in the face guard, and the 311-pounder deftly wrapped his hands around the ball and rumbled for an 18-yard score.

"That doesn't happen every week, that's for sure," Kevin Williams said. "It's highly unusual, but you've got to remember we've got some talent up front. You saw that today."

EXTRA POINTS: Vikings running back Adrian Peterson missed two recent games with a knee injury but said he felt fine during a quiet game against the 49ers. "There was one play where I felt it, but it wasn't anything serious," he said. "I came out for a play and shook it off." ... 49ers kick returner Maurice Hicks had two 55-yarders in the second quarter. His career long is a 64-yard effort against the Arizona Cardinals last Dec. 24. ... The 49ers had seven tackles behind the line of scrimmage and four tackles for no gain against the top rushing team in the NFL. In all, the Vikings managed just 54 total yards in the second half. ... To reach 1,000 yards for a second consecutive season, running back Frank Gore will need to average 73 yards per game over the 49ers' final three. ... The 49ers opened with a 4-3 defense for the first time this season.