MILWAUKEE -- After all the care the Twins took with Josh Donaldson’s health in Spring Training, it took one batted ball for his luck to run out.

Donaldson exited in the first inning of the Twins’ Opening Day matchup against the Brewers with right hamstring tightness after running gingerly into second base on a double to left-center field -- and though Byron Buxton’s late two-run homer nearly carried them to victory anyway, a ninth-inning rally against the newly signed Alex Colomé only compounded Minnesota’s woes in a 6-5, 10-inning loss at American Family Field on Thursday.

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The Twins will use their scheduled off-day on Friday to get Donaldson some treatment, evaluate his condition and decide on a further course of action.

“Obviously, there has to be some concern, but we’ll wait and see until we know a little bit more to comment further,” manager Rocco Baldelli said.

Though Donaldson’s right calf was the problematic muscle that caused him to miss extended time last season, the Twins believe that this isn’t a recurrence of that injury

“I haven't heard, actually, anything calf-related from the time we took him out of the game until now,” Baldelli said. “It looks like it's isolated to his hamstring area.”

Donaldson had been locked in throughout Spring Training, with 10 of his 19 tracked batted balls hit in excess of 100 mph, and his bat stayed hot with a 112.1 mph line drive into the left-center-field gap in his first plate appearance of the season. He sprinted out of the batter’s box and rounded first base, but then he appeared to slow down and limp on his way to second. Donaldson remained on the basepaths, but he didn’t emerge from the dugout to play defense in the bottom of the first.

Luis Arraez moved in from left field to take Donaldson’s place at third, and Jake Cave entered to play left.

The Twins have been open about the fact that Donaldson’s health is one of their priorities this season after the 2015 American League MVP Award winner -- now in the second year of a four-year, $92 million contract -- was held to only 28 games last season and missed the playoffs due to recurring issues with his right calf, which have been a persistent concern throughout his 10-year career.

In the interest of keeping the 35-year-old Donaldson on the field, the Twins made adjustments to his strength and conditioning regimen, helped him alter his running mechanics, gave him a late start to Spring Training and were even expected to limit his usage early in the regular season. Not even Donaldson knew before Opening Day how many games he could have expected to play this year, but Minnesota was expecting to evaluate how he felt after several games.

He didn’t make it that far -- and now, the Twins will once again have to reckon with the possibility of life without one of their cornerstone players on both offense and defense.

If Donaldson were to require a stint on the injured list, Arraez could be a candidate to take over as the everyday third baseman, or Miguel Sanó could move across the diamond with Brent Rooker filling in at first base.

Minnesota immediately caught a glimpse of the impact of that in a lengthy third inning, when Arraez couldn’t handle a two-out slow roller down the third-base line off the bat of Avisaíl García that could have ended a Brewers threat against Kenta Maeda. Donaldson might have fared better on such a play, but Arraez, playing out of his natural second-base position, couldn’t make the barehanded pickup.

That might have cost the Twins 15 pitches and a run, as Travis Shaw then worked an eight-pitch, bases-loaded walk against an uncharacteristically wild Maeda -- only the second run-scoring free pass of his career.

The defense didn’t get any better from there, and it cost the Twins the game.

Five of the Brewers’ six runs on Thursday were unearned, and the new-look Twins defense struggled in its first test. Andrelton Simmons committed a rare error in the fifth inning by dropping a double-play throw from Sanó, eventually allowing a run to score. With a three-run lead in the ninth, Colomé made a costly mistake with an errant throw to second base instead of getting the sure out at first -- and on the next play, Christian Yelich’s liner to right field went in and out of Max Kepler’s glove for an RBI single.

García’s ensuing groundout might otherwise have ended the game, but the Brewers still had enough life for Travis Shaw to tie the game with a two-run, two-out double. One inning later, they walked it off.

“It was kind of a combination of things that happened that obviously didn’t go our way, and we didn’t make the plays that we needed to,” Baldelli said. “I’m not saying they were all very straightforward plays, but we had a pretty good opportunity to win the game.”

Still, that was one game out of 162, and the manner in which the Twins hit and pitched for most of it didn’t offer much for concern.

“If we battle like that and play like that all year long, I think we’re going to be in a good spot,” Baldelli said. “Today did not go our way, but our guys played with good enthusiasm. It was a good-looking game for the vast majority of the game, and we were really happy with where we were sitting.”

Donaldson’s injury, on the other hand, could again have a cascading impact if serious -- and the Twins will need to wait and see how big that impact could be.