River Falls, Wis. ? Will Shields missed another day of practice Saturday because of back trouble, and Kansas City Chiefs coach Dick Vermeil said he was concerned about his 10-time Pro Bowl guard.

Shields, a 13-year veteran, waffled during the offseason about whether to retire or play one more year. He said in an interview Thursday that his hesitation “was more physical than anything else.”

Vermeil said Shields would see another doctor for a third opinion on his back problem. Asked if he was worried Shields might not play this year, Vermeil said, “I think you always have to have a little concern.”

He said it was not a disc problem that bothered the 6-foot-3, 320-pounder.

“Will has always had a little back problem,” Vermeil said. “He’s got a little arthritis at the very bottom of his back, and it pinches a nerve, and all of a sudden it grabs him.”

Vermeil said doctors believed the problem could be resolved “with patience and proper exercise, what they call back stabilization exercises.”

“A veteran like Will Shields, we would only be working him one a day anyway,” Vermeil said. “I think there was a period of time when Will was not sure what he wanted to do in terms of coming back, so that influenced his offseason preparation as well.

“I think he’s always been much further along in his preparation to play the league opener than he is right now.”

Shields has indicated this would be his final year. Losing him would be a blow to what has been one of the NFL’s most stellar lines. After being taken in the third round out of Nebraska in 1993, he immediately established himself as one of the finest guards in the league. His string of 10 straight Pro Bowl selections is the longest current streak in the NFL.