After spending a significant amount of time as a starting pitcher, Siegrist converted to relief full-time for 2013.

For his rookie year, Siegrist posted a 0.45 earned run average (ERA) in 39+2⁄3 innings pitched (IP), striking out 50.

He appeared in ten games for Batavia, making one start and earning a victory while posting an overall season 3.86 ERA.

He began the season in the Class A Midwest League with the Quad Cities River Bandits starting nine games, winning eight of them, and posting a low 1.15 ERA.

[4] Siegrist fared less well after promotion to the Palm Beach Cardinals back near his Florida home, going 0–3 in eleven games as his ERA jumped to 3.42.

[3] Another year, another split season as Siegrist spent 2012 with Palm Beach before advancing to the Double-A Springfield Cardinals.

A combined 7–2 record between the two teams, including 6–0 with Palm Beach, and 68 strikeouts over 87 IP[1] caught the attention of officials with main club as the St. Louis Cardinals added Siegrist to their 40-man roster after the 2012 season.

Instead of grooming him to be a starter, the Cardinals predicted he would have a velocity increase as a full-time reliever, and as a left-hander, could serve as a valuable late-inning strategic piece.

[3] He quickly moved up to the Triple-A Memphis Redbirds of the Pacific Coast League, where he spent just 7+2⁄3 IP after four years between the Rookie and A levels.

[7] He made his major league debut the same night as he took the mound in the 7th inning in relief of Shelby Miller in a game against the Arizona Diamondbacks at Busch Stadium.

[12] Siegrist earned his first major league save by pitching the last two innings of a 6−1 win against the Cincinnati Reds on April 17.

On October 4, Siegrist was removed from the 40–man roster and sent outright to the Triple–A Lehigh Valley IronPigs, but he rejected the assignment and elected free agency.

[21] On July 2, 2022, Siegrist signed with the Charleston Dirty Birds of the Atlantic League of Professional Baseball.

According to Brooks Baseball, throws over 90 miles per hour (140 km/h) with his fastball, generating a high number of swings and misses.