Yet when it comes to how his career is judged in the end, numbers could be his greatest, most objective piece of support. For all the headlines, the outspoken remarks and the team changes that have served as the backdrop for his two decades in the Major Leagues, it's the numbers -- unopinionated, emotionless statistics -- that show the impact he has had on the field.
With his 500th home run -- he stands six away -- the impact will be resounding. Homers don't tell nearly the whole story of Sheffield as a hitter. He feels RBIs are the more important numbers for a player's worth, and his selectiveness at the plate has set him apart from most power hitters. Still, homers are about to put him in some exclusive company.
Sheffield's .293 career average would rank higher than half of the 24 members of the 500-homer club. He needs one stolen base for 250, a milestone only three 500-homer members have reached. His .395 on-base percentage would rank in the top 10 among his soon-to-be colleagues. And only Ted Williams and Mel Ott have 500 homers with fewer strikeouts.
"Sounds like Hall of Fame to me," Sheffield's current manager, Detroit's Jim Leyland, said recently.
It reflects one quality that numbers can't quantify. That's the incredible drive that has constantly pushed Sheffield throughout his career, including today.
"I've played with all the best in the game," Sheffield said. "I've outplayed all of them. Whatever team I was on, I always said I'm going to outplay the best player on this team. And I did that."
It's the type of company Sheffield was almost expected to join as soon as he broke into the Majors as a 19-year-old Milwaukee Brewer in 1988. He was a Little League World Series participant in 1980, a high school star in the early half of the decade in Tampa, Fla., and a first-round Draft pick in 1986.
He had incredible athletic ability, but he also had an instinct for the game that couldn't be taught.
"He was one of those guys who grew up, probably 5 years old when he started playing the game, with tremendous instincts," said Mariners manager Jim Riggleman, who managed Sheffield in San Diego in 1992-93. "You couldn't get a fastball by him, he had a great knowledge of the strike zone, and he probably is the best right-handed hitter I have seen."
It took a while for that ability to shine, and it didn't come until he popped up with the Padres. From the day he arrived in Milwaukee, he was a star, and it followed him on the field. His talent was obvious over four years with the Brewers, but so were injuries and controversies. And aside from his lone full season of play in 1990, the numbers didn't emerge.
He was traded just before Opening Day in 1992, and his career took off from there. He went from an underage superstar in Milwaukee to another star player among many in San Diego, including his good friend Fred McGriff, and he believes that made a major difference.
"I got into the right situation in San Diego," Sheffield said. "I happened to be with the right team, right surroundings, right manager, right type of players. Everything was right. And they allowed me to just go play baseball. I didn't have to answer questions. Tony Gwynn did that. All I had to do was play baseball."
He never hit .300 in Milwaukee, but he won a batting title with a .330 average his first season with the Padres. He beat out Gwynn, among others.
"Gary and Tony Gwynn, from the left side, are probably the two best hitters I ever managed," said Riggleman, whose players under his charge in his career have included Ichiro Suzuki, Sammy Sosa, and of course, McGriff.
He didn't get a chance to manage him much longer. A slow start and payroll concerns led to a fire sale, and Sheffield was among the biggest pieces. Sheffield was on the move again, headed to Florida for a prospect package that included a promising young reliever named Trevor Hoffman.
Soon after he arrived, then-Marlins president Dave Dombrowski told a concerned Sheffield to be patient, that they were going to build a winner. That patience paid off. He enjoyed the best statistical season with the Marlins in 1996, batting .314 with 42 home runs, 120 RBIs, 142 walks and just 66 strikeouts. But it was the year after, when his numbers dropped with a star-studded cast around him, that he finally reached his goal of a World Series championship.
He has been seeking another title ever since, and he has bounced from city to city in the process. The 1998 dismantling of the Marlins' roster sent Sheffield to the Dodgers that summer. Three years later, he was dealt to Atlanta when talks on a contract extension fell apart. After two seasons with the Braves, he joined the Yankees in a famous handshake agreement with owner George Steinbrenner.
When he was dealt to Detroit two years ago, it marked his seventh Major League team. As he pointed out, though, there are a lot of factors that go into moving around.
"I allowed [the Marlins] to trade me to accommodate other people," Sheffield said. "I could've been selfish and said, 'No, I want to stay in one place.' So there's a lot of factors involved in why I've gone to different teams. I could've stayed with the Braves. I produced, but I left the team because they didn't want to pay."
The production is the key term. Through all his stops, all the headlines, Sheffield has produced. The only opponent that has slowed him is the injury bug. A dozen stints on the disabled list, several surgeries on his shoulders, a nasty wrist injury with the Yankees two years ago and age have taken their toll as time has gone on, not to mention all the times he has played hurt.
"If Gary Sheffield had not had the surgeries he had and missed some time," Riggleman said, "I have no doubt in my mind he would have challenged -- probably not overtaken, but he would have challenged -- Hank Aaron's numbers. ... His numbers, as great as they are, would be right now, at 40 years old, he probably would be looking at 650 (home runs) right now."
It's highly unlikely he'll get that far now, but with a few more home runs, he'll have a place in history. And once he's out of the limelight, gone from the headlines, he can let his numbers do the talking.
Jason Beck is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.