Chicago — Tyler Alexander kept waiting for the punch line.

Doug Mientkiewicz, Toledo Mud Hens manager, called him into the office after Monday night's game and told him he was going to make his next start Wednesday. Which he knew. But it would be in Chicago, with the Tigers, against the White Sox in the second game of a doubleheader.

Which Alexander thought might be some cruel prank.

“I didn’t believe him,” said Alexander, a lefthander who has been grinding in the Tigers system since 2015. “I stood there for a while, like, ‘You serious?’ It was an awesome moment. It’s a dream.”

The dream was nearly deferred. The Tigers and White Sox were rained out on Tuesday night — meaning Matthew Boyd's start would be pushed back. Had it been pushed to Wednesday, Alexander's debut would be pushed back or cancelled.

Instead, Boyd will pitch Thursday, pushing Gregory Soto's next start to Saturday.

The make-up date for Tuesday's rainout will be Sept. 27, part of a straight double-header beginning at 4:40 p.m. Detroit time.

Alexander, who was twice drafted by the Tigers, once out of high school, then in the second round in 2015 out of Texas Christian, will be added to the roster as the 26th man for Wednesday's second game.

“At no point did I think I was going to get called here,” he said. “I had no clue. I knew they were down a guy, I knew they had four starters and then they went down to three — but it never crossed my mind.”

Ryan Carpenter and Kyle Funkhouser, two pitchers who might have been higher on the organizational depth chart, have fallen off recently. Alexander has had his ups and downs as well, but his 12-strikeout game against Rochester on June 22 opened some eyes.

“He attacks the zone,” said catcher Bobby Wilson, who caught him in Toledo. “He’s not scared of anything. He’s not scared of one thing. He’s going to attack hitters.”

Alexander, who throws from a deceptive arm slot, features a low-90s fastball, a slider and a change-up. He gave up five runs in three innings in his last start, but he pitched 13 2/3 consecutive scoreless innings in his two starts before that.

“He’s easy to root for, easy to get behind,” Wilson said. “He puts his head down and he gets to the grind of things. You have a lot of respect for people like him who are the underdogs, who don’t complain or make excuses and just keep working and trying to get better.”

Triple-A hitters posted a .350 average against Alexander in the first two months of the season. In June, they hit .234 with 33 strikeouts in 28 innings.

“The first two months were tough,” he said. “I was finding a new arm slot and trying to make adjustments to the new balls (same balls that are being used in the major leagues this season) we’re using. But our pitching coach, Juan Nieves, worked with me a lot.

“We put in a lot of work and things just started to click.”

The first person he called with the news was his father.

“I don’t think my dad believed me either,” he said, laughing.

The Tigers will add Alexander to the 40-man roster before Wednesday's game. A corresponding move will be necessary.

Mercer is back

It wasn’t like he had to reintroduce himself to his teammates, but it had to feel like opening day all over again for shortstop Jordy Mercer.

He was activated off the injured list and back in the starting lineup for the first time since May 7.

“It means everything,” he said. “I miss the camaraderie. I miss the guys — that’s the biggest thing. Obviously, I miss playing. But you miss the brotherhood, you miss the family. You miss just being back on the field trying to help your team win.”

Mercer, whom the Tigers signed to a one-year, $5 million contract during the offseason, had played just 19 games. He first injured his right quad in April and missed two weeks. He played five games in May and then aggravated it and has been out since May 7.

“It’s something I never had to experience,” he said. “It’s made me a better person. It’s made me a better father. I’ve had a lot of time to reflect and I think it’s going to make me a better player. I know how to deal with this now.

“Sometimes life throws you a curveball. You deal with it and come out the other end a better person.”

What about Goodrum?

Mercer's return brings a much-needed veteran presence to the middle of the Tigers defense.

“The stability in the infield is really important,” Tigers manager Ron Gardenhire said. “He’s a good communicator and a leader out there. With all the shifts and everything we do, he understands it pretty good.

“It’s been a long time without him. We were playing pretty good early when we had him. It’s just nice to have a veteran back in the middle.”

That’s not to discredit the job Niko Goodrum did filling in at shortstop in June. The more he played, the more comfortable he became. But it took a toll on him physically.

“This lets us put Goody in different situations, which was the plan all along,” Gardenhire said. “We need to give guys a break here and there. Goody played a lot of baseball and he got beat up pretty good. … I'd rather be able to give him a day off like everybody else.

“But it’s hard not to put him in the lineup. We’ll just keep moving him around.”

Goodrum got the start at second base Tuesday.

Tigers at White Sox

First pitch: Game 1, 2:10 p.m.; Game 2: 8:10 p.m.; Guaranteed Rate Field, Chicago

TV/radio: FS1, FSD, 97.1

SCOUTING REPORT

Game 1

LHP Daniel Norris (2-7, 4.62), Tigers: He grinded out five solid innings against the Nationals in his last start, despite dealing with a cramp in his groin. He made back-to-back starts against the White Sox in April, going five innings both times. He shut them out in Comerica Park, but allowed four runs and 10 hits in Chicago.

RHP Dylan Cease, White Sox (MLB debut): This will be the major league debut for one of the top White Sox pitching prospects — No. 3 in their system, No. 18 overall. He features an upper-90s fastball and a firm, sinking curveball. He came to the White Sox in the deal for Jose Quintana in 2017.

Game 2

LHP Tyler Alexander, Tigers (MLB debut): Alexander, who has made a steady, under-the-radar climb through the Tigers system, will be added to the roster as the 26th man and make his big-league debut. He features a low-90s fastball, slider and change-up.

LHP Ross Detwiler (1-0, 3.60), White Sox: The 11-year veteran has been signed out of Independent League baseball the last two years and hasn’t spent a full season in the big leagues since 2015. When he beat the Twins on Saturday, it was his first big-league win since 2016.

Twitter.com: @cmccosky