Javier Alfonso López Palmer (born July 11, 1977) is a Puerto Rican former professional baseball pitcher.

He pitched in Major League Baseball (MLB) for the Colorado Rockies (2003–05), Arizona Diamondbacks (2005), Boston Red Sox (2006–09), Pittsburgh Pirates (2010), and San Francisco Giants (2010–16).

He is currently a member of the Giants broadcast team, working alongside Dave Flemming as color commentator for their away games.

López attended the University of Virginia, earning a degree in psychology despite leaving early to begin his baseball career.

He began his career as a starting pitcher but struggled, and was converted into a sidearm (or submarine) reliever while still in the Diamondbacks' organization.

Before the 2003 season, he was selected by the Boston Red Sox in the Rule 5 draft, but was traded to the Colorado Rockies during spring training.

He spent all of 2003 on Colorado's roster, nearly tying the franchise record for most consecutive batters retired and finishing third among major league rookies in games pitched.

In 2006, he signed with the Chicago White Sox but failed to make the team and spent the first part of the season in the minors before getting traded to Boston during the year.

He posted a 15.43 ERA in the playoffs but won his first World Series ring as the Red Sox defeated Colorado in four games.

Through June 2022, he was one of 38 former UVA players to have made it to the major leagues, along with Mark Reynolds and Ryan Zimmerman among others.

Despite leaving college after only three years to play professional baseball, López continued working on his degree in psychology, which he earned in 2002 to fulfill a promise to his father-in-law.

He was promoted to the El Paso Diablos of the AA Texas League that season, where he had a 1–0 record, a 7.42 ERA, 21 strikeouts, and 40 innings pitched in 22 games (one start, his last professionally).

[11] He got his first major league strikeout in his next game on April 5, punching out Tony Womack in a 4–3 victory over the Diamondbacks.

[16] He played in 72 games, the third-most among rookies in the major leagues, trailing only Óscar Villareal (86) and Brad Lidge (78).

[7] He was called back to the majors on August 10 to replace an injured Aaron Cook and played the rest of the season in Colorado.

[6] López began 2005 with the Rockies, but after allowing five runs in his first three games (for a 22.50 ERA), he was optioned to Colorado Springs on April 11.

[7] López made the Red Sox' Opening Day roster in 2007, but after four scoreless outings he was optioned to Pawtucket on April 9 to make room for Mike Timlin, who had started the season on the disabled list.

[29] On this stint, he posted a 3.18 ERA in 40 appearances before getting sent down on August 5 to make room for Curt Schilling, who was returning from the disabled list.

[6] López made the playoffs for the second year in a row as the Red Sox won the AL Wild Card.

[38] He made two appearances in the AL Championship Series (ALCS) against the Tampa Bay Rays, allowing no runs as the Red Sox were defeated in seven games.

[41] On May 10, López was designated for assignment to make room for pitcher Daniel Bard after he started the year 0–2 with a 9.26 ERA in 14 games.

He made two appearances in the NLDS against the Atlanta Braves to face Jason Heyward, whom he struck out both times.

[49] López made two appearances against the Texas Rangers in the 2010 World Series, striking out the two batters he faced.

In Game 2, he struck out Josh Hamilton to end the top of the eighth inning with a runner on second and preserve a 2–0 lead, although the Giants went on to win 9–0.

He and Brad Ziegler were the only relief pitchers in the major leagues to toss at least 50 innings without allowing a home run.

[33][60] López recorded his only save of the 2013 season on September 19, pitching the final 2⁄3 of the ninth inning in a 2–1 victory over the Mets.

Lopez won his fourth World Series ring as the Giants defeated the Kansas City Royals in seven games.

[64] Along with teammate Brandon Crawford, López won the Willie Mac Award, which honors the Giants' most inspirational player.

[72] After López struggled to begin his professional career, throwing over the top, he decided he needed to change his style.

[4] In the Diamondbacks' system in 2002, with the help of Mike Myers, he began throwing sidearm (or submarine), which Andy Baggarly called "a decision that changed his life.