While in the minor leagues, Mazzilli set a California League record (and what is believed to be a professional record) when he stole seven bases in a game for the Mets' minor league affiliate Visalia against San Jose on June 8, .
In , Mazzilli led the Mets with 181 hits, and 79 runs batted in, and was their sole representative at the All-Star Game in Seattle. Mazzilli hit a home run to tie the game in the 8th, and walks in the 9th to bring in the winning run of the National League's 7–6 victory. However, Dave Parker, with two outstanding throws, is named the MVP. The following year, he had his best statistical season, leading the Mets with 162 hits, 31 doubles, 16 home runs, 76 RBIs, 82 runs, and 41 stolen bases.
Following the season, where he hit only .228 and was hampered by injuries to his back and elbow, he was traded by the Mets to the Texas Rangers. Though initially unpopular with Met fans, the deal would prove to be a good one, bringing minor league pitchers Ron Darling and Walt Terrell in return. Darling would go on to be a key starter on Mets' World Series championship team, while Terrell was traded to the Detroit Tigers for another important player on that team, third baseman Howard Johnson following the 1984 season.
Mazzilli played only 58 games with Texas and was traded to the Yankees for Bucky Dent midway through the 1982 season. Prior to the 1983 season, Mazzilli was traded to the Pirates for Tim Burke, Don Aubin, John Holland and Jose Rivera.
The Mets were early favorites to reach the post season in 1986, and prior to the start of the season offered third baseman Ray Knight to the Pirates for Mazzilli. The Pirates turned them down, but as destiny would have it, the Pirates released him in July, 1986, and he re-signed with the Mets on August 3.
Upon signing with the Mets, Mazzilli was assigned to their triple-A affiliate, the Tidewater Tides. Interestingly enough, this was his first tour of duty with the Tides as he had made the jump to the major leagues from double-A. On August 7, the Mets released left fielder George Foster and called Mazzilli up to the majors. Foster was very critical of this move by the Mets, and accused his former employers of racism.
Mazzilli turned out to be an important part of their championship team. His career with the Mets continued until when he was claimed by the Blue Jays on waivers. Mazzilli retired after the 1989 season, his 14th in the Major Leagues.
|Team||Year||Regular Season||Post Season|
|Games||Won||Lost||Win %||Finish||Won||Lost||Win %||Result|
|BAL||2004||162||78||84||.481||3rd in AL East||-||-||-||-|
|BAL||2005||107||51||56||.477||4th in AL East||-||-||-||-|