In 2001, Snell split the season between the GCL Pirates and the Short Season-A New York – Penn League Williamsport Crosscutters.

Snell played the 2002 season with the South Atlantic League Champion Hickory Crawdads, a Single-A club.

In 2003, when Snell went 14–4 with a 3.00 ERA and 145 strikeouts in 26 minor league starts, split between Single-A Lynchburg and Double-A Altoona, he was named the Pirates organizational Pitcher-of-the-Year.

In his debut, he surrendered one hit (a solo home run to John Mabry), three walks and two strikeouts in two innings of work.

[3] On March 16, 2008, Snell agreed to a three-year contract extension with the Pirates worth at least $8 million, including club options for 2011 and 2012.

[8] On July 29, 2009, Snell and shortstop Jack Wilson were traded to the Seattle Mariners for Jeff Clement, Ronny Cedeño, Aaron Pribanic, Brett Lorin, and Nathan Adcock.

On July 31, the Mariners recalled Snell to take the roster spot of pitcher Jarrod Washburn, who had been traded earlier that day.

After teammate Doug Fister went on the DL, Snell took over his roster spot, therefore returning to the rotation, and in his next two starts, he proceeded to go 0–2 with a 12.86 ERA.

On June 9, Snell had a career-worst start where he pitched only 1.2 innings, giving up eight runs (seven earned), one walk, and struck out only one in a 12–2 loss to the Texas Rangers that dropped him to 0–5.

[10] On January 14, 2011, Snell signed a minor league contract with the St. Louis Cardinals the deal included an invite to spring training.

[12] In April, he decided to reconsider retiring and the Cardinals released Snell to allow him to pursue any opportunities.