CHICAGO -- The initial reactions to Frank Thomas were about what he couldn't do. That soon changed to the things he did which were unlike any other, and it eventually evolved into a Hall of Fame career.

Thomas will be inducted Sunday into the Baseball Hall of Fame in Cooperstown, N.Y. It will be a celebration of a groundbreaking career that saw him win two MVP awards and compile a .419 career on-base percentage that is third-best all-time among right-handed hitters.

Frank Thomas, a two-time AL MVP, hit 521 home runs during his 19-year career. Ron Vesely/MLB Photos via Getty Images

But when Thomas first took the field in the minor leagues as a first-round draft pick (seventh overall) by the White Sox in 1989, some questioned whether he would even make it to the big leagues to show off his offensive prowess.

"I didn't know he was great right off the bat because the first time I saw him was in A-ball and I had doubts that he could play first base," chairman Jerry Reinsdorf said. "When I saw him play, it looked like he didn't know where first base was."

Thomas managed to figure out some subtle nuances around the bag, although defense never was his strong suit. He simply hit so well that he was able to overcome any defensive liabilities he had, and moving to the designated hitter spot only increased his overall productivity.

When he arrived in the major leagues in 1990, his unique approach at the plate was on full display.

"You're looking at it and you're thinking, at that time you didn't see big guys that get a base hit the other way and walk," former Thomas teammate and current White Sox manager Robin Ventura said. "He had the power, but you're just talking about the smaller part of the game, where back then it was just swing as hard as you can and see how far you're going to hit it. But he took his walks, he didn't like striking out, and that was a change at that time for somebody his size."

Interestingly, the walks and the base hits the other way came early, but the home runs did not.

"I remember the first month he was up here he didn't hit a home run, and so we were wondering, 'Does this guy really have power?'" Reinsdorf said. "But after a couple of years he started putting up numbers like (Lou) Gehrig and (Jimmie) Foxx and (Mel) Ott and (Babe) Ruth. You knew if he stayed healthy he'd get into the Hall of Fame."

The time has arrived for the Hall of Fame to open its door to Thomas, and clearly he is worthy of the honor.

Paul Konerko played with Thomas for seven seasons (1999-2005) and calls Thomas the best hitter he has ever seen.

"That year in 2000, up close, that's about as good as I've seen anybody just kind of dominate," Konerko said. "Even his outs, nothing looked bad. Maybe one at-bat out of every 15 it was a bad at-bat. It's pretty hard to do for six-month period."

Thomas batted .328 in 2000 with a 1.061 OPS, but finished second in the MVP voting to Jason Giambi, who later admitted that performance-enhancing substances were part of his early-career routine. Assuming Thomas would have added a third MVP award if Giambi hadn't cut corners only enhances his Hall of Fame credentials.

Thomas was in the Hall of Fame argument when he left the White Sox after the 2005 season, and he seemed to print his ticket to Cooperstown when he delivered a .926 OPS with 39 home runs and 114 RBIs with Oakland in 2006, finishing fourth in the MVP voting.

"I don't think anyone questioned whether he still had it, it was all injury; that gets people at the end of their career," Konerko said. "He had a couple of those, ankle or foot, where if he can get it healthy there was no question whether he would hit or not. That's different than playing healthy and not doing the job. We never really saw that from Frank.

"If he didn't hit well, it was related to injury. When he came back that year with Oakland, as long as he could swing the bat, the numbers would be there. It was that simple."

Thomas was simply so good with the bat that he got everybody to forget what he couldn't do with the glove.

"I just know watching Frank, I thought he was the greatest right-handed hitter I've ever seen," Reinsdorf said. "Now I think he's one of the three greatest because I think (Miguel) Cabrera and (Albert) Pujols are probably in that category. Still, that's pretty special. I didn't see (Rogers) Hornsby so I don't know how good he was."