Mark William Prior (born September 7, 1980) is an American former professional baseball pitcher and current coach. A onetime top prospect of the Chicago Cubs, he pitched for the team from 2002 to 2006 in a career that was marred by injuries. In his prime, his repertoire of pitches included a mid-90s mph fastball, a curveball, and a changeup. He is the pitching coach for the Los Angeles Dodgers.
Born and raised in San Diego, California, Prior engaged Tom House as his pitching tutor in high school. A career at the University of Southern California, where he won the Golden Spikes Award, saw him become one of the top prospects in the 2001 MLB draft, when he was the second overall pick by the Cubs. He made only nine appearances in the minor leagues before debuting with the team in 2002. In 2003, he finished third in National League (NL) Cy Young Award voting, ranking among the leaders with 18 wins, a 2.43 earned run average (ERA), and 245 strikeouts. Helping the Cubs win the NL Central title, he outpitched Greg Maddux in the NL Division Series and won Game 2 of the NL Championship Series, but he was on the mound for Game 6 when Steve Bartman prevented Moisés Alou from catching a foul ball.
Prior had pitched a scoreless game up to this point, but the Florida Marlins went on to win the series in seven games after an eighth inning eight-run rally in that game, in which Prior received the loss. In 2004, he was on the disabled list twice but finished the season with a 16-strikeout performance against the Cincinnati Reds. He made 27 starts with the Cubs in 2005 and finished ninth in the NL in strikeouts despite missing some time due to injury. Multiple injuries limited him to nine games in 2006, and he did not pitch at all in 2007 due to tears in his labrum, anterior capsule, and rotator cuff. After the season, the Cubs non-tendered him, letting him become a free agent.
Prior never pitched in the major leagues again after that, though he tried several times. He pitched in the minor leagues for multiple organizations over the next six years before finally retiring at the end of the 2013 season. Once touted as having "perfect" pitching mechanics by ESPN and others, his "Inverted W" arm action has been discussed as a possible reason for his lack of durability, as well as Dusty Baker's heavy usage of him during the 2003 season, though Prior himself does not blame Baker for his injuries. Prior accepted a front office position with the San Diego Padres in 2013, then joined the Dodgers in 2018 as a bullpen coach, becoming their pitching coach in 2020. He has been a part of three World Series-winning clubs since joining the Dodgers, in 2020, 2024 and 2025.
Amateur career
Born September 7, 1980, in San Diego, California, Prior was part of an athletic family. Jerry, his father, played college football for Vanderbilt University, and both of Mark's older siblings played sports as well. "Being the youngest of three kids, there's no room for me to step out of line," he quipped. Tim Corbin later compared him to David Price and Kris Benson. He then transferred to the University of Southern California (USC), posting a 10–7 record his sophomore year and leading the USC Trojans to the 2000 College World Series. USC posted a 16–game winning streak before Prior helped USC reach the College World Series again in 2001, posting a 15–1 record and a 1.69 earned run average (ERA), striking out 202 in innings while walking just 18.
Professional career
Chicago Cubs
In 2001, Prior re-entered the draft and was considered "the consensus top player", according to ESPN. He was taken second overall by the Chicago Cubs, behind Joe Mauer, who was drafted by the Minnesota Twins. The Cubs signed Prior to a contract for $10.5 million, the highest signing bonus for a draft pick until the Washington Nationals gave Stephen Strasburg $15 million in 2009.
After nine starts in the minors, Prior was called up to the big leagues in 2002 as a 21-year-old. On June 7, he threw 128 pitches and struck out 11 while allowing no runs in a 2–0 win over the Seattle Mariners. He threw his first career complete game on August 4, striking out 13, allowing one run, and throwing 136 pitches in a 4–1 win over the Colorado Rockies. "I was kind of surprised that they did send me out there," he said, when he found out he was pitching the ninth. On August 15, he struck out seven hitters in a row, tying the Cubs' record shared by Jamie Moyer and Kerry Wood. In total, he struck out 12 in six innings, earning a no decision in an eventual 6–4 win. During a game against the St. Louis Cardinals on August 31, he was removed because of a strained left hamstring. Two days later, the Cubs announced they were shutting him down for the rest of the year because of the injury. Prior finished his rookie campaign with a 6–6 record with a 3.32 ERA, and 147 strikeouts in innings pitched. The Sporting News called his rookie season "stellar", and he finished seventh in National League (NL) Rookie of the Year Award voting. In six innings on May 12, he allowed four runs to the Milwaukee Brewers but struck out 11 and earned the victory in an 11–5 triumph. He struck out 16 Brewers on June 26, allowing two runs in eight innings but getting a no decision in a 5–3 loss.