Milwaukee Brewers

In 2005, he was drafted by the Milwaukee Brewers in the 20th round of the 2005 Major League Baseball Draft. He played for the Rookie-League Helena Brewers. He was promoted to the Class-A West Virginia Power in 2006, where he was tied for the South Atlantic League lead with one shutout. He was placed on the disabled list on 2 June with back spasms and was reinstated on 15 June.

Welch's 2007 season was spent with the Class-A Advanced Brevard County Manatees where he allowed the fewest baserunners per game by a starter in the Florida State League (FSL). He recorded the ninth-lowest ERA (ERA) with a 3.43 clip in the FSL. He allowed the second-fewest walks per nine innings and fifth-best ERA as a starter in the FSL. He went 6–7 with a 3.43 ERA in 29 games, 20 starts, and led the team in innings pitched with 1202⁄3 innings. He was placed on the disabled list on 13 April with a concussion and was reinstated on 23 April.

Welch spent the 2008 season with the Double-A Huntsville Stars. He went 11–4 with a 3.90 ERA in 26 games, all starts. He had one shutout. Welch played all of the 2009 season in Huntsville. He was released by the Brewers during spring training 2010.^[1]

Sydney Blue Sox

Welch was an integral part of the Sydney rotation along with Chris Oxspring. He finished the regular season with a league best 5–0 record with a 1.44 ERA. Welch threw a no-hitter against the Adelaide Bite in game one of the preliminary final series, the first in Australian Baseball League history.^[2]

David was expected to resign either in the US, Japan or Korea during 2011,^[3] but on 18 July 2011 announced his retirement from professional baseball.^[4]