Examples in baseball are pretty easy to come up with and here's one: What if Major League Baseball had found out about Ty Cobb and Tris Speaker fixing that game in September 1919 immediately upon its occurence? Maybe Cobb gets banned from baseball (no-one much liked him anyway), and maybe the Black Sox, afraid to throw anything in the publicity aftermath, never turn black; Joe Jackson and Eddie Cicotte never get banned from the game. Maybe Jackson, with the deposed Cobb and Speaker out of the way, becomes the all time hits leader, and becomes a real rival with Babe Ruth for the public's affection; then becomes the most popular player in the wake of Ruth's infamous 1925 season, when the Babe couldn't hit, got drunk and had that infamous bellyache. Maybe Jackson hits .400 a couple of times, and the White Sox challenge the Yankees each year for the American League championship. And since the owners never had to hire famed racist Judge Kennesaw Mountain Landis, maybe the color line gets broken by a young Josh Gibson, and not by Jackie Robinson. Think how different things could be!
Anyway, I'm sure that there exists a world somewhere where Dave Hajek won the Astros third baseman job out of '96 spring training. Sure the Astros had traded Raul Chavez and Dave Veres to get Sean Berry the previous December, but Hajek himself was coming off a 1995 AAA All-Star game appearance (and in fact would make another in '96), and there were questions (well-founded as it turned out) about Berry's defense. Nothing was written in stone, is what I'm trying to say here. Hajek had hit .327 at Tuscon in 1995, .324 there in '94 and .292 at Jackson in 1993. Plus he was a low K guy, only once having struck out more than 30 times in a season. He was a guy who could have had a lot of success as a major leaguer. And in another world, he did.