As a starting pitcher, he played in Major League Baseball (MLB) for the Chicago Cubs, Philadelphia Phillies, and San Francisco Giants.

He has been a television and radio broadcaster for the Giants since 1990, and is one half of the popular "Kruk and Kuip" duo, alongside his friend and former teammate Duane Kuiper.

Though his collegiate eligibility was cut short, he still holds the school record for career earned run average at 1.94, and is tied for most shutouts in a season with five.

[3] The trade helped Philadelphia win the National League pennant in 1983, but it also gave San Francisco two pitching arms that would become a big part of the Giants' success in the late 1980s.

Although known as a starter, Krukow earned his only career save on August 31, 1984, pitching to just one batter (the Phillies' Sixto Lezcano), inducing a game-ending groundout, therefore preserving a 6–5 Giant victory.

Krukow was the winning pitcher in a nine-inning complete game, allowing two runs on nine hits, as the Giants beat the St. Louis Cardinals, 4–2.

Krukow went 4–3 with a 3.98 ERA during a 1989 campaign which was cut short on June 30 when he underwent arthroscopic surgery to repair a rotator cuff tear in his pitching shoulder after spending parts of three seasons on the injured list for what was believed to be bursitis.

[9][10] He was ninth in Giants franchise history with 66 wins and sixth with 802 strikeouts at the time of his retirement as an active player on March 19, 1990 due to recurring shoulder problems.

[11] "Kruk," who was named as the starting right-handed pitcher to the 1980s Giants All-Decade Team in a vote by Bay Area media in 1999, is noted for his deep knowledge of the game and tremendous sense of humor.

[14] According to sportswriter Steve Fainaru, Krukow "blew it off... for years", but "secretly feared he had amyotrophic lateral sclerosis, Lou Gehrig's disease".

[15] Because of increasing hand weakness that limits his ability to play stringed instruments, he has recently taken up the drums, which require a different set of muscular movements.