Justin Morneau's back started bothering him last August. He missed six days of games before returning to first base on Aug. 24.

Morneau played the next 18 games in pain and with terrible production. He was 7-for-63 (.111) with two home runs and six RBI. There were more tests on the back, and he was diagnosed with a stress fracture.

The Twins were 70-72 and in third place, 5 1/2 games from first, after Morneau played his last game on Sept. 12. They won 16 of 20 to tie Detroit at the top of the AL Central, then won the memorable Game 163 playoff in the Metrodome.

Morneau's missed time was a substantial contrast to the previous three seasons, when he was the Twins' ironman. He played 157 games in 2006 and '07. Then, in 2008, he became the 32nd player to appear in 163 or more games -- dating to the expansion of the schedule from 154 games in 1961.

"Morney never wanted to come out," Gardenhire said. "We had to give him off days. And that was the plan this spring -- not to go after it so hard in spring training, and give him a few off days during the season."

Gardenhire was able to stick to that strategy, even though Morneau was his only hitter who could be classified as "hot" through the first half of the schedule. The Twins played Game 84 on July 7 in Toronto. At that point, Morneau had been given three days off and also was ill and restricted to pinch hitting in two games in Oakland.

Morneau was kneed in the head by Toronto's John McDonald while trying to break up a double play. He left the game because of what turned out to be a concussion and hasn't played since.

The Twins were 45-39 and third place, 1 1/2 games from first, after that loss in Toronto. They have gone 22-11 in the 5 1/2 weeks that followed and have taken over first place, two games in front of the White Sox.

"It doesn't matter how many games we've won without Morney," Gardenhire said. "I think about how many more we would've won if we had him."

The manager let that hang for a moment, then added: "When he's in the middle, I always feel better about our lineup. He's always going to be there: 30 home runs, 100-plus RBI, a .300 average and outstanding defense.

"Cuddy [Michael Cuddyer] is a good first baseman, not great. Morney is as good as there is at first ... makes the whole infield better."

Morneau was batting .345 with 18 home runs and 56 RBI when he took the knee to the head. Thirty-two games later, he still was one in front of Jason Kubel for the team lead in home runs and fourth in RBI.

The Twins had been experimenting with Cuddyer at third base in order to get Jim Thome in the lineup against righthanded starters. Cuddyer went back to right field and rookie Danny Valencia played third against lefties.

Cuddyer has played all 33 games at first base since Morneau's concussion. The Twins had a moment of panic on Wednesday in Chicago, when Jose Mijares was late huffing to first and collapsed in the dirt because of what proved to be a torn meniscus in his right knee.

A few feet away, Cuddyer was making a dive toward first in an attempt to tag the bag, and the White Sox' Carlos Quentin required a long jump to clear him.

Cuddyer's first base tenure will continue indefinitely. Morneau revealed Friday that he was yet to have a symptom-free day, making it sound as if his return could be weeks away.

Valencia and Thome will remain the main beneficiaries in at-bats during Morneau's absence. Valencia has been a regular at third base and Thome can serve as the DH with no extra maneuvering.

The stats during Morneau's absence: Valencia -- 31-for-99 (.313), one home run and 15 RBI in 25 games; Thome -- 18-for-66 (.273), five home runs and 10 RBI with 19 starts at DH.

Those are competitive numbers, but Gardenhire admitted this before Saturday's game:

"They aren't Justin Morneau numbers. You aren't going to totally replace one of the best hitters in baseball."

Patrick Reusse can be heard noon-4 weekdays on 1500ESPN. • preusse@startribune.com