Twins first baseman Joe Mauer left Friday night’s game after the top of the fifth inning when a nagging neck injury flared up.

Mauer had suffered a slight injury to the left side of his neck while chasing after then diving for a foul ball during last weekend’s series in Anaheim. He continued to play, while treating it, over the next several days.

“It’s kinda more left but kind of the whole back/neck,” Mauer said. “Like I said, I’ve been getting treatment on it the last couple days. Today it just got worse so we thought it was the best move.”

Mauer was replaced by Logan Morrison, who was the third batter up in the fifth inning.

Mauer, batting .283 after going 0-for-2 on Friday, doesn’t expect to be out long.

“Day to day,” he said. “I’d like to be in the lineup tomorrow to be honest. It might take a day or two. Nothing more than that. I just think I need to let it calm down.”

Sano to Rochester

Miguel Sano is heading to Class AAA Rochester to begin a minor league rehab assignment. The slugger has reached the point where he can take the next step in his recovery from a strained left hamstring.

After working out before Friday’s game, Twins manager Paul Molitor expressed optimism that Sano had finally gotten over the hump and is ready to start swinging a bat. After the early session, Sano met with team trainers and the club nutritionist to plot a course for his return to games.

“I thought he looked significantly better,” Molitor said. “Even as early as Wednesday. Better effort means less pain.”

Sano has been working out on the side for a couple weeks, but unable to run hard because of the lingering soreness in the hamstring. The club brought Sano on the recent four-game road series to Anaheim, but saw someone who was tentative when trying to run hard.

It has taken longer than expected for Sano to run harder. He has also spent time going through conditioning drills.

On Friday, Sano belted batting practice pitches out to every part of Target Field.

Since Aug. 19 of last season, Sano has played in just 23 of 81 games. The Twins surged to the wild-card round without him last season but have only played well in spurts this season. So his absence has been felt in some capacity.

May’s progress

Righthander Trevor May, coming back from Tommy John surgery, gave up one run over four innings on Thursday for Class AAA Rochester in his first minor league rehabilitation start. He gave up three hits and walked two while striking out five.

Looks like a solid first outing. But there’s more to it.

With Brad Steil, the director of professional scouting, looking on, May threw all his pitches and the movement looked familiar. So the Twins were pleased from that aspect. But May has to work on maintaining his velocity.

His fastball averaged 90.5 mph, with a high of 92.6 and low of 87.9. He threw 29 pitches over 90 and 11 under 90.

“It was a good step,” Molitor said. “He got to his number — 60 pitches. And we’ll try to extend him to 75 next time out.”

Etc.

• The Twins wore their red uniform tops Friday. And, no, it wasn’t righthander Kyle Gibson’s idea. The Twins have decided to wear the uniform during Friday home games. The old-school looking ivory uniforms — let’s call them Killebrew classics — are worn on Wednesdays and Saturdays. The starting pitcher can choose the uniform the other four days of the week.