Early in the 2007 season, Maestri's second season of professional ball with the Class A Peoria Chiefs, he gave up seven runs in two innings against the Cedar Rapids Kernels. From that point on, he did not give up more than two runs in an appearance for the rest of the season, and converted his first seven save opportunities to earn himself a Midwest LeagueAll-Star nod.
His success in 2007 prompted the Cubs to try to convert Maestri into a starter. Thus, he began the 2008 season in the starting rotation of the Florida State League Class A advanced Daytona Cubs. In this role, he went 5-3 with a 3.69 ERA to again earn himself an All Star nod. Following the all star game, Maestri was promoted to the double A Southern LeagueTennessee Smokies. With the Smokies, Maestri made two starts in which he pitched 11 innings and gave up eight earned runs before shoulder soreness forced the Cubs to shut him down for the remainder of the season, and ended the Cubs' experiment with Maestri as a starter.[2]
On November 5, 2011, Maestri made his Australian Baseball League debut with the Brisbane Bandits. Starting against the Canberra Cavalry, Maestri went five innings and gave up two hits, picking up the first win of the Bandits' 2011-12 season. His performances earned him a spot with Team World at the 2011 Australian Baseball League All-Star Game. Maestri pitched a scoreless inning in the game. Maestri continued the season as the Bandits' ace, finishing third highest in the league in strikeouts and innings pitched. The Bandits ended the half a game short of the playoffs, with Maestri posting a 3.25 ERA and a 1.16 WHIP en route to winning the ABL's Fan Choice Award.
Maestri signed with the Orix Buffaloes of Nippon Professional baseball prior to the 2012 season.[6] In his first season with Orix, Maestri recorded a 4–3 record and 2.17 ERA with 40 strikeouts. In 2013, Maestri pitched to a 7–5 record and 5.40 ERA in 24 games. In 36 games in 2014, Maestri registered a 3–1 record and stellar 1.97 ERA with 48 strikeouts. In his final season with Orix, Maestri recorded an 0-2 record and 3.19 ERA in 28 games.
On November 9, 2015, Maestri elected free agency.[7]
Hanwha Eagles
In 2016, Maestri moved to the Hanwha Eagles of the KBO League.[8] He was released on June 25, 2016, to make way for new signing Fabio Castillo. He had recorded a 9.42 ERA in 9 games for the Eagles.[9]