Following two sub-par seasons, Thomas lost a close MVP vote in 2000 despite posting career highs of 43 home runs and 143 RBI.

Later in Thomas's career, a variety of foot injuries and minor ailments reduced his productivity and often limited him to a designated hitter role.

In 2005, his final season in Chicago, he was limited to only 34 games after starting the year on the disabled list and then fracturing a bone in his foot close to where it was surgically repaired the previous off-season.

Thomas spent the final three years of his career with the Oakland Athletics and Toronto Blue Jays, with whom he hit his 500th home run.

By the end of his career, Thomas was tied for eighth in AL history for home runs (521), ninth for RBI (1,704), and sixth for walks (1,667).

Highlights included a three-homer game in Wareham, as well as a home run over the 434' sign in center field at Eldredge Park in Orleans.

The Chicago White Sox selected Thomas with the seventh pick in the first round of the June 1989 Major League Baseball draft.

[8] He made his major league debut on August 2, 1990, against the Milwaukee Brewers at County Stadium; he went without a hit, going 0-for-4, but had an RBI on a fielder's choice which scored Iván Calderón as the White Sox won the game 4–3.

[11] Thomas became known for his menacing home run power; in the on-deck circle, he routinely swung a rusted piece of rebar that he reportedly found during a renovation project in Old Comiskey Park.

[12] In his first full season, Thomas established himself as a multi-talented hitter, combining power with hitting for average, drawing walks, and driving in runs.

[11] He joined a quartet of Hall of Famers (Babe Ruth, Lou Gehrig, Jimmie Foxx and Ted Williams) as the only players in baseball history to eclipse .300 with more than 20 homers and more than 100 RBI, runs, and walks in three straight seasons.

"[citation needed] White Sox announcer Ken Harrelson echoed the praise, "In my 30 years in the game, I've never seen anyone like Big Hurt [Thomas].

[14] In 1994, playing just 113 games due to a strike-shortened season, Thomas again put up huge offensive numbers, batting .353 with 38 homers and 101 RBI, and he led the league in runs scored (106), walks (109), and slugging percentage with a whopping .729 mark.

[15] He is one of only three first basemen in history to win consecutive MVP awards in the major leagues (Hall of Famer Jimmie Foxx, 1932–1933, and Albert Pujols, 2008–2009, are the others).

Never a defensive standout at first base during the early part of his career, Thomas nonetheless preferred playing in the field to serving as a designated hitter, saying that it kept him focused; the fact that he did generally hit better as a first baseman created a dilemma over the years for the White Sox as to whether to use him as a DH, which would reduce wear on his body but might cost some offensive production.

In 2001, after his father died, Thomas also announced during the same week that he would undergo season-ending surgery after an MRI revealed a triceps tear in his right arm.

In 2005, Thomas again suffered from injury, but hit 12 home runs in 105 at-bats over 35 games, demonstrating his continued power at the plate.

As a member of the White Sox, Thomas and teammate Magglio Ordóñez tied a major league record for back-to-back homers, with six in one season.

Despite his perennial offensive production and established fan base in Chicago, the White Sox elected to release Thomas in 2005.

Thomas later expressed disappointment with how his 16-year tenure with the White Sox was ended, saying that chairman Jerry Reinsdorf did not call him to tell him he wasn't coming back.

Moments later, when he hit his first home run of the night to put his former team behind in the score 1–0, the Chicago crowd gave Thomas a standing ovation.

[11] On October 7, 2006, Thomas finished behind Jim Thome, his replacement as the White Sox's DH, in the voting for the AL Comeback Player of the Year Award.

[37] The following day, with the bases loaded and a 2–2 tie, Thomas hit a grand slam off Red Sox reliever Manny Delcarmen, leading the Jays to a 7–4 victory.

[43] After playing 55 games with Oakland due to time on the disabled list, Thomas hit five more home runs to bring his career total to 521, while posting a .263 batting average.

There are only six other players in history who have both hit more home runs and have a higher career batting average than Thomas: Ted Williams, Hank Aaron, Jimmie Foxx, Babe Ruth, Manny Ramirez, and Willie Mays.

Thomas implied that he stopped using them after the collective bargaining agreement between the union and the league regulated teams' travel schedules.

[51] In a 2018 interview with the Chicago Sun-Times, Thomas complained that his "career was stepped on" by competitors who used PEDs and "was the most hurt" of any players in that era.

[55] Thomas was elected to the National Baseball Hall of Fame in 2014 with 83.7% of the vote in his initial year of eligibility, and was inducted as a member of the White Sox on July 27, 2014.

Baseball (as a hot-prospect rookie wearing #68 named Ricky Davis who forces Tom Selleck's character off the Yankees roster).

[63] In June 2023, Thomas joined Apple TV+'s Friday Night Baseball coverage as an occasional interviewer and color commentator.