– Paul Molitor’s warning was prescient.

“I always say good baserunning can be a momentum-changer,” the Twins manager said before Thursday’s game, when asked of Eddie Rosario’s full-speed-ahead approach to capturing extra bases. “It can work adversely, too.”

It certainly can. The same go-for-it instinct that compelled Rosario to race from first to an uncovered third base, catching Toronto third baseman Yangervis Solarte off guard Wednesday — “Some guys have the feel, the awareness and the anticipation that the risk is worthwhile,” Molitor said approvingly — can also short-circuit a scoring opportunity when he gets too overaggressive.

Which is what happened Thursday. Rosario, having drawn a one-out walk in the sixth inning with the Twins trailing Boston 1-0, easily reached third base ahead of Jackie Bradley’s throw when Brian Dozier singled to center, sliding head-first into the base. But he wasn’t done.

When third baseman Rafael Devers threw to second base to try to retire Dozier, who opportunistically moved up a base, Rosario saw second baseman Brock Holt make an awkward catch, with his back to third. So he jumped to his feet and decided to try to score.

Big mistake. Rosario was easily thrown out, and a second-and-third, one-out threat suddenly became a one-on, two-out situation that fizzled on a Robbie Grossman ground out.

But Molitor said he was OK with the play, though it would have been a better risk had there been two outs.

“He’s going to do those things. Unfortunately, the slide he made into third may have cost him a step or so in getting his break. But he almost caused an errant throw,” said Molitor, who added Rosario’s decision-making is greatly improved this year. “If you win by a run, you’d be singing his praises.”

There’s not much a third-base coach can do with such an impulsive runner, though. Joked Gene Glynn of the play, “I missed my tackle.”

‘Seeing the ball better’

Mitch Garver served as the Twins designated hitter Thursday, delivering the go-ahead two-out double in the eighth inning off Matt Barnes. Garver’s start wasn’t entirely a product of his 7-for-10, five-RBI hot streak in Toronto.

The rookie catcher had made a positive impression even before going on this tear, mostly by making better contact — not just hitting the ball harder, but more often.

“There’s no question he’s seeing the ball better,” Molitor said. “He’s laying off some pitches he was chasing earlier.”

The numbers bear that out. Garver had a strikeout rate of 32.6 percent as a rookie, and it wasn’t much better early this season — 30.2 percent when Jason Castro went on the disabled list May 15. But handed a chance to play more frequently, Garver set about improving his plate discipline.

His strikeout rate is 22.4 percent since then, and he has whiffed only nine times since June 20, a 15.5 percent rate that is a big part of the reason he is getting at-bats even when he is not behind the plate.

“I’m just trying to keep a consistent approach,” Garver said. “I want to hit the ball hard, not hit it anywhere in particular.”

More rehab for Reed

The Twins sent righthanded reliever Addison Reed to Class AAA Rochester on Thursday to serve a rehab assignment. Reed, out since July 10 because of tightness in his right triceps, had been expected to be activated during this road trip after throwing effectively in bullpen sessions this week.

“It just seems like the proper thing for him, long-term. I know he’s anxious to help us,” Molitor said. “We talked it through, and this seems like the best option to make sure we don’t go backwards, as far as all the progress we’ve made over the last two and a half weeks.”

Etc.

• The Twins put off center fielder Byron Buxton’s return to Rochester’s roster by one more day, deciding his strained left wrist could use another session of batting practice.

• Nathan Eovaldi, acquired Thursday by Boston from the Rays for lefthander Jalen Beeks, will make his Red Sox debut Sunday vs. the Twins. Eovaldi, who gave up eight runs in 2⅔ innings July 13 at Target Field, will take the place of Drew Pomeranz.