ST. Paul (Pioneer Press )  For Twins fans eager to add another proven starter to the 2020 rotation, there was doubt Thursday. For those who thought their team was crazy to trade a 21-year-old pitcher who regularly hits 100 mph on the radar gun, there was hope.

An eye-opening, three-team trade set into motion late Tuesday reportedly hit a snag on Wednesday when the Boston Red Sox got a look at the medical records of top Twins pitching prospect Brusdar Graterol, according to The Athletic.

The deal has never been confirmed by the Twins, Red Sox or Los Angeles Dodgers, who had agreed to send right-handed starter Kenta Maeda, via Boston, to Minnesota.

The Twins did not immediately return messages Thursday morning.

Ken Rosenthal reported the Red Sox were surprised to learn that Graterol, who made his major league debut last season, is not in ideal shape to join a starting rotation.

Graterol, who had Tommy John surgery to repair his right elbow at 16, was placed on the injured list with a shoulder impingement last season and missed more than two months at Class AA. He was called up to the big-league club in September and pitched 10 games relief, going 1-1 with a 4.66 earned-run average.

He struck out 10 and walked two in 9 2/3 innings and set the franchise velocity record with pitches of 101.2 and 101.9 mph against the Cleveland Indians on Sept. 15. In the Twins’ three-game playoff loss to the New York Yankees, Graterol pitched one inning, striking out two.

According to Rosenthal, the Boston-Minnesota piece to the 10-player trade is the final holdup on a deal that would send Red Sox center fielder Mookie Betts and left-handed pitcher David Price to Los Angeles, and outfielder Alex Verdugo and Maeda to Boston — and ultimately Minnesota.

Maeda, 31, went 10-8 with a 4.04 ERA in 37 games (26 starts) for the Dodgers last season. Signed through 2023 at $3 million a year, he struck out 169 batters and walked 51 in 153 1/3 innings last season. He would join a rotation with Jose Berrios, Jake Odorizzi, Michael Pineda and Homer Bailey or Rich Hill.

Pineda will be unavailable until mid-May because he has 39 games remaining on a suspension — he tested positive last season for a banned diuretic — and Hill is still rehabbing from surgery to repair his left elbow. His best-case scenario return is mid-June.

In four major-league seasons, Maeda is 47-35 with a 3.87 ERA. Of his 137 appearances, 103 were starts. He pitched his first eight professional seasons with the Hiroshima Toyo Carp of Nippon Professional Baseball.