All of the previously mentioned players were very poor free-agent signings, but none came anywhere close to how bad Oliver Perez was for the Mets.
Acquired from the Pirates in 2006, after the Duaner Sanchez taxi cab accident, Perez did not pitch particularly well for the rest of the season, but had two solid starts in the NLCS against the Cardinals, with the latter occurring in Game 7. The Mets did not win that game in the end, but Perez certainly gave them a chance.
Perez then went 15-10 with a 3.56 ERA in 2007 and surprised a lot of people while doing so. He had a knack for pitching well against good teams and pitching poorly against teams that were not as good.
In 2008, Perez went 10-7 with a 4.22 ERA. However, he led the National League in walks with 105, and had more control issues than before.
Perez was a decent pitcher at that time, but after the Mets decided to overpay him with a new three-year, $36 million contract, he instantly became the most useless pitcher, if not player, in baseball.
Perez's 2009 season was mostly lost due a recurring knee injury, but when he was on the mound, it was not a pretty sight. In just 14 starts, he went 3-4 with an alarming 6.82 ERA. The Mets even tried to not have him pitch often, but when he did, the games were forgettable.
After the 2009 season, Mets fans were hoping that Perez would get released or traded. Neither of the two happened in the following offseason and Perez remained a Met in 2010. He was moved to the bullpen in May of that year, and became clearly selfish when he repeatedly refused any minor league assignments, which only made his teammates and the fans dislike him more and more.
After refusing an assignment for the second time, Perez was placed on the disabled list. After being activated, he only made six more appearances after July 21, all in relief, and all in blowout games. He was fittingly the losing pitcher in the final game of the season.
Once Sandy Alderson became the new general manager, he finally took action during the 2011 Spring Training and released Perez, thus ending Perez's time as a Met. The Mets ate the remaining $12 million left on his contract while doing so. Perez later signed a minor league contract with the Nationals, but did not make a major-league appearance in 2011.