Piñeiro began the baseball season as a promising starting pitcher for the Seattle Mariners. The previous two years he started in 60 games, won a total of 30 games, and produced a 3.52 ERA. 2004 though, turned into a dismal year with Piñeiro posting a 4.67 ERA and the first losing record of his career. Piñeiro suffered another problem when he was placed on the disabled list July 27, 2004, with a sore elbow and subsequently missed the remainder of the season. Piñeiro continued his struggles in and was optioned to Triple-A Tacoma on May 14, 2005. He returned to the majors and started in 30 total games; however he was unable to return to his previous form and posted a 5.62 ERA for the year. In, Piñeiro was pulled from the starting rotation again on August 26, and placed in the bullpen. His 6.36 ERA was the highest in the major leagues. Following the 2006 season, the Mariners declined to tender Piñeiro a contract offer, making him a free agent.
On January 3,, he reached an agreement for a one-year deal with the Boston Red Sox, where he struggled as a member of the bullpen. On July 22, he was designated for assignment in order to clear a roster spot for Jon Lester. Piñeiro cleared waivers and accepted an assignment with the Pawtucket Red Sox, Boston's Triple-A affiliate, where he returned to the starting rotation.
St. Louis Cardinals
On July 31, 2007, Piñeiro was traded to the St. Louis Cardinals, with cash considerations, for a player to be named later. In his debut start with the Cardinals on August 4 vs. the Washington Nationals, he pitched 5 innings, giving up 7 hits, 5 runs, 2 walks, 2 strikeouts, 1 home run while taking his second loss of the year in the Cardinals 12–1 loss. In his debut home start with the Cardinals on August 9 against the San Diego Padres, he out-pitched Chris Young, giving up only 4 hits, 0 runs, 0 walks, and earning 4 strikeouts, lowering his ERA to 4.50 for the year in winning his second game with the Cardinals in their 5–0 win. For the rest of 2007, Piñeiro showed some flashes of promise but general inconsistency, finishing with a record of 6–4 and posting an earned run average of 3.96 for his new team. 2008 was a season typified by inconsistency and a trip to the DL, as Piñeiro allowed home runs and 180 hits in IP, posting a 7–7 record and 5.15 ERA. However, leading into 2009, Piñeiro reinvented his approach, utilizing a sinking fastball to pitch to contact and concede more ground balls, while limiting the number of home runs allowed. In 32 starts, Piñeiro posted a 15–12 record with a 3.49 ERA and led the major leagues with 1.1 walks per nine innings rate. After the 2009 season, Piñeiro filed for free agency.
On January 22, 2010, Piñeiro signed a 2-year, $16 million deal with the Los Angeles Angels of Anaheim. Because of Piñeiro's volatile performance before the 2009 season, critics were split on the deal, with most wondering whether his sinkerball would continue to be effective in 2010. Taking the sinkerball as starting point, Fangraph's Dave Allen thought, "the price was solid." Baseball Prospectus's Christina Kahrl pointed out the different starters that failed after leaving Cardinals pitching coach Dave Duncan's guiding hand. "There are so many unknowns that it makes the proposition that he'll deliver on this deal seem dubious", concluding "this just doesn't seem like it'll go well." Meanwhile, ESPN's Rob Neyer said quality was not so important as quantity: Piñeiro would be worth the contract if he would just pitch 200 innings per season. His first season was cut short due to injury, starting only 23 games. The following season was met with another trip to the disabled list. He finished 7-7 in 27 games.
On January 15, 2012, Piñeiro signed a minor league deal that included an invitation to Spring Training with the Philadelphia Phillies. Piñeiro was released on March 19, 2012, after just six innings in Spring Training.
Piñeiro signed a minor league contract with the Baltimore Orioles on April 11, 2012. Piñeiro did not pitch for their organization due to a shoulder injury. Piñeiro re-signed with the Orioles for the 2013 season on a minor league contract.
Piñeiro signed a minor league contract with the Chicago Cubs on April 1, 2014. On June 6, 2014, Piñeiro was released by the Cubs.
Second stint with the Angels
On June 7, 2014, Piñeiro signed a minor league deal to return to the Angels, less than a day after being released by the Cubs. He was released on June 30, 2014, after being suspended 50 games for testing positive for a banned stimulant.
On May 9, 2015, Piñeiro signed a minor league contract with the Toronto Blue Jays. He was assigned to the Double-A New Hampshire Fisher Cats, and later the Triple-A Buffalo Bisons. In 13 appearances, Piñeiro posted a 5–4 record, 4.23 ERA, and 35 strikeouts in 76 innings pitched. He was released on July 22.
Personal life
Piñeiro resides in Río Piedras, Puerto Rico with his wife Shirley and children Joel, Jr., Juliana, and twins Adrian & Fabian.
