There’s a great line in Taxi when Tony (the aspiring boxer) gets a fight with a much more successful boxer.
Tony: “This guy’s good. I looked up his record.”
Elaine: “And…”
Tony: “He’s so good, you can look up his record.”
I don’t remember all the details, but Karras had some kind of gambling scandal during his football career. That may have been why he was slow to be elected to the Hall.
Ed O’Neill (Married with Children and Modern Family) was signed to the Pittsburgh Steelers in 1969 (Chuck Noll’s first year as head coach), but was cut from the team during training camp. He was up against Mean Joe Greene for a spot on the defensive line, so perhaps it’s understandable that he didn’t make it.
He did; he was suspended for the 1963 NFL season for gambling on NFL games. OTOH, another star player, Packers RB Paul Hornung, suffered the same suspension, for the same reason, over the same season, and was elected to the HoF in 1986.
That said, it may well have been a factor.
Woody Strode, Bernie Casey, Tommy Lee Jones, Burt Reynolds and John Wayne all played football in college and/or professionally before gaining some some measure of fame as actors.
ETA - Mike Mazurki played football as well before going into pro wrestling and then acting. And if pro wrestling counts as a sport, then we could add Tor Johnson.
How would you count ballet dancers, like Gillian Murphy or Herman Corñejo of American Ballet Theater, two of my current favorites?
They’re performers, artists, and I would argue that’s the main thing they are. But for pure athletic skill and agility they would have to rank right up there with any professional athlete.
Anyway, I’m voting for Gillian Murphy. I’ve seen her dance Giselle twice and both times were among the most powerfully emotional and downright beautiful experiences of my life.
Bob Uecker
While he was a poor hitter, he was considered a fine defensive catcher and he did last six years in the majors.
And he homered off Koufax.
Not a surprise: Dwayne Johnson / The Rock was both a pro wrestler and a college football player on a national championship team.
Surprise: Tommy Lee Jones was an offensive lineman on the Harvard football team.
Bigger surprise: Woody Allen was a good baseball player on his high school team.
Well I am aware that he did a lot of scoring.
(Uggh)
Comedian Eddie Izzard, who’s also acted in plenty of comic and dramatic roles, is an accomplished long distance runner, once running 43 marathons in 51 days.
A poor hitter in the major leagues still means he was one of the best baseball players in the country.
His fame and acting career was a direct result of his sports career. He went from playing to being the Brewers radio announcer. His acting didn’t happen until later after his off the cuff humor while announcing games made him well known. He became a favorite of Johnny Carson and was a frequent guest on the Tonight Show. Then he started to get other gigs.
If we’re counting dancers then Mikhail Baryshnikov springs to mind.
Another Ivy League football star was Dean Cain. He was a good enough free safety at Princeton to be signed by the Bills after graduation. He doesn’t quite fit because he was relatively well known while he was playing. He large number of interceptions was being followed in the press. Possibly because he was also the boyfriend of Brooke Shields
Pretty sure he was a massive international star as a dancer before he ever acted. This thread is looking for those who are famous as actors/musicians/performers but were also great athletes. But their athletic performance did not make them famous.
Also Alexander Godunov, a ballet dancer who defected from the USSR. He had small parts in Witness and in Die Hard. Sadly, he died at age 45 from complications due to chronic alcohol abuse.
Kareem of course was a legendary player. Doesn’t fit. Same with Crabbe and Weismuller. Both were picked for the job because they were famous athletes.
When Ed Marinaro came on Hill Street Blues I immediately knew him as the guy from the Jets. Michael Warren is an interesting case. His basketball career was largely forgotten. He was outshined by the legendary players on the team like Kareem and also his legendary coach. He also never made it to the pros mostly because he was too short. But he was a leader on that UCLA team. He was captain of the team for two years. He was pretty integral to the team but everyone remembers Kareem and then Bill Walton and the championship streak.
Billy Joel said in one interview that taking piano lessons earned him jeers, taunts, whatever as a kid, so he took boxing lessons.
Joel reluctantly began piano lessons at age four at his mother’s insistence.[13] His teachers included the noted American pianist Morton Estrin[18] and musician Timothy Ford. Joel says that he is a better organist than pianist.[19] As a teenager, Joel took up boxing so he could defend himself.[20] He boxed successfully on the amateur Golden Gloves circuit for a short time, winning 22 bouts, but abandoned the sport shortly after his nose was broken in his 24th boxing match.[21]
(Hence the cover on “The Stranger,” it seems).
I guess Gabe tried to make it in baseball but failed. However, remember this?
Starting at the 8:00 mark, Gabe Kaplan defeats Robert Conrad in a foot race on Battle of the Network Stars
They cut him even though he scored four touchdowns in one game when he was in high school, including the game winner against his nemesis “Spare Tire” Dixon? 
James Caan played football at Michigan State. He had dreams of being a pro but was undersized. He took the role in Brian’s Song as an attempt to impress the pros and maybe get on the team. The movie had a lot of the actual Chicago Bears players and staff in it.
Schwarzenegger?
Weightlifting is not a sport that requires any skill. The Olympic lifts(Clean and Jerk, Snatch) require balance, strength, speed and agility but the lifts enhance athletic fitness but don’t enhance specific skills.