NEW YORK -- Arizona Diamondbacks prospect Daniel Vasquez was one of four players suspended Friday for violating the Minor League Drug Prevention and Treatment Program.

Also receiving 50-game suspensions were free agent catcher Matt Tupman, pitcher Jefferson Segundo of the St. Louis Cardinals organization and pitcher Joel Tamares of the Florida Marlins organization.

Vasquez was banned after testing positive for metabolites of Stanozolol, a performance-enhancing substance, according to the Office of the Commissioner of Baseball. The 23-year-old right-hander was 4-1 with one save and a 4.57 ERA in 29 games, including one start, for Class A South Bend in 2009.

Tupman was suspended for a second positive test for a drug of abuse. The 30-year-old catcher started last season with Triple-A Omaha in the Kansas City Royals organization and ended it with Double-A Mobile in the Diamondbacks organization. He combined to hit .256 with a homer and 26 RBIs in 59 games.

Segundo was suspended after testing positive for metabolites of Stanozolol. The 20-year-old right-hander was 2-0 with one save and an 8.04 ERA in 12 games, including one start, in the Rookie-level Dominican Summer League.

Tamares was suspended after testing positive for Boldenone, a performance-enhancing substance. The 19-year-old right-hander went 1-3 with a 3.29 ERA in 10 games, including four starts, in the Dominican Summer League.

The suspensions to Vasquez, Segundo and Tamares are effective at the start of the 2010 season. Tupman's ban begins as soon as he signs with a Major League organization.