Top pitching prospect Stephen Gonsalves to make Twins debut Monday

Such is the cycle of baseball: One significant Twins career might have come to an end Sunday, but a new one may be a day away.

Stephen Gonsalves, the top lefthanded pitching prospect in the Twins farm system, was summoned from Class AAA Rochester and handed the daunting task of replacing, perhaps permanently, 2017 All-Star Ervin Santana. Gonsalves will make his major league debut Monday vs. the White Sox, in front of 30-40 friends and family members flying across the country from his San Diego home.

"I was in bed already" when the call came late Saturday night at the team hotel in Toledo, Ohio. "I was shocked. The first person I called was my grandmother, and shared some tears with her. We're all very excited."

The Twins are too, manager Paul Molitor said, because Gonsalves has been a consistent winner — he's 53-20 with a 2.46 ERA in six minor league seasons — practically from the moment he was drafted in the fourth round in 2013. He was the Twins Minor League Pitcher of the Year in 2016, and has ranked on the team's top-10 prospect lists for three years.

"He's never been a particularly hard thrower … but the combination of using an elevated fastball, even at lower velocity, still plays for him with his deception," Molitor said. "He's got really good secondary pitches that he's going to need at this level."

Walks have occasionally been a problem, but he has given up only 76 hits in 120 minor league innings this year. Trouble is, he has walked 65, to go with 120 strikeouts.

"I was struggling a little bit, walking everyone," he said. "For the past month, I haven't been walking as many. It was more of a mental block instead of mechanical."

Santana was placed on the disabled list, but it felt a lot more like a farewell. The pain in his right middle finger, operated on in February, still lingers when he grips a ball, and even worsened as he made five starts, with disappointing results, since July 25.

"Sometimes it feels good, sometimes it doesn't," said Santana, who has an 8.03 ERA and whose fastball has averaged only 89.3 miles per hour since rejoining the team. "You need to get it right before you do anything else. I'm going to shut it down and try to recover as fast as I can."

But the Twins, far outside the postseason race and eager to give playing time to players a decade younger than Santana's 35 years, might not be in any hurry. They feel a responsibility to the veteran, whose four-year, $55 million contract expires in November, "to support him the best way we can," Molitor said. But "there's a component of 'what makes sense for us' that's going to be in there, too."

The Twins are almost certain to pass up Santana's $14 million option for 2019 — they will pay him a $1 million buyout instead — and go with a younger rotation next year. Santana, 30-25 with a 3.68 ERA with the Twins, will be a free agent, coming off a career-worst season.

• Alan Busenitz was called up to take Santana's roster spot Sunday. Afterward, the Twins returned righthander Tyler Duffey to Rochester to make room for Gonsalves. Outfielder Robbie Grossman was activated from the disabled list, after proving with a 5-for-12 rehab stint over the weekend that his right hamstring is healthy again.

• Third base coach Gene Glynn felt ill before Sunday's game and was sent home.