Born in Hamtramck, Michigan, Gromek originally began playing professionally with the Indians organization as an infielder, but became a pitcher early on, and made his major league debut in 1941.

His career is best remembered for a post game celebratory photo taken of him hugging Larry Doby, the first black player in the American League, whose third inning home run provided the margin of victory.

[3] In his first professional season, Gromek batted .283 with two home runs as a second baseman for the Mansfield Braves and Logan Indians.

Meanwhile, back-to-back home runs by Roy Cullenbine and Pat Seerey in the fourth inning gave Cleveland a 2–0 lead.

[16] He ended the season winning six of his final seven decisions, finishing the year with a 10–9 record with a 2.56 ERA, and had a league leading 7.1 hits per nine innings.

[19] In late August, Gromek won his 16th game in a 5–4 victory against the Detroit Tigers, but injured his knee when scoring the winning run, causing him to miss two weeks.

[8] After getting married in the offseason, Gromek entered the 1946 season as one of the four primary starting pitchers alongside Allie Reynolds, as well as Bob Feller and Red Embree who had returned from the war.

After his June 28 win, however, Gromek fell in a slump, and Indians management reduced his role to that of a part-time starter who would only see action in a few innings at a time.

[24] Gromek lost seven straight games between June 28 and September 10 before breaking the streak in his second-to-last appearance of the season, a 4–2 victory against the Yankees.

One of his first jobs was to work with Gromek during the offseason and improve his pitching due to his struggles the prior year, in particular against left-handed batters.

[30] After a second complete game victory against the Athletics on July 15, Gromek was moved to a part-time starter role, where he remained the rest of the season.

Gromek, meanwhile, held the Braves scoreless with the exception of a Marv Rickert home run in the seventh inning, giving the Indians the win by a final score of 2–1.

Doby had just broken the color barrier in the American League a season earlier, and resistance to integration in baseball was still intense.

[1][34] In his Hall of Fame acceptance speech, Doby fondly remembered that picture: That was a feeling from within, the human side of two people, one black and one white.

By the end of May, he had an ERA of 2.80, which was among the lowest on the team, but only had a 2–4 record to show for it due to a lack of run support; the four losses included both a 1–0 and 2–0 defeat.

With the increased productivity of Early Wynn and Mike Garcia, Gromek fell out of favor with Boudreau, and he was moved primarily to relief duty.

The highlight of his season came on May 28 against the Chicago White Sox, throwing a 7–0 complete game shutout, dropping his ERA on the year from 7.98 to 4.94 in the process.

He struggled in spring training, but he was not considered in danger of losing his role to a rookie, as López felt that he knew what Gromek could and could not do on the mound.

On June 15, after pitching in five games for the Indians, he, Al Aber, Ray Boone and Dick Weik were traded to the Tigers for Owen Friend, Joe Ginsberg, Art Houtteman and Bill Wight.

[45] In the case of both Gromek and Houtteman, it was thought that a change of scenery would benefit both players as both had been inconsistent in recent years, so the two were added into the trade package.

[46] In his first appearance upon joining his new club, Gromek allowed nine earned runs in one inning in a 23–3 blowout loss to the Boston Red Sox.

Despite the poor first outing, Tigers manager Fred Hutchinson decided that the veteran Gromek's best fit would be as a starter with his staff of young pitchers.

[47] His confidence paid off, as Gromek shut out Philadelphia in his next appearance, allowing four hits and cementing his role in the starting rotation for the rest of the season.

[52] On May 9, his complete game eleven inning victory over the Chicago White Sox improved Gromek's record to 5–0 with a 1.72 ERA, making him the first pitcher in the league with five wins.

In the ninth inning, Athletics pitcher Marion Fricano, who had a reputation as a head hunter himself (two days prior, he ended the Chicago White Sox's Cass Michaels' career with a beanball),[55] retaliated and threw at Gromek's back.

[58] He finished the season with 13 wins and 10 losses and a 3.98 ERA in 28 appearances, and led the league with 26 home runs allowed for the second straight year.

[8] Gromek was pulled in the third inning in his first start of 1957 and spent the rest of his tenure with the Tigers as a short-term reliever; in a May 2 game against the Red Sox, he was brought in solely to face one batter, Jackie Jensen.

[61] Due to arm trouble, he was released by the Tigers in August, and subsequently retired, finishing the year with a 6.08 ERA in 15 appearances.