But with their 40-man roster at 39, the D-backs on Monday claimed Tatum, who was once again on waivers, from the Astros.
The D-backs have Miguel Montero and Henry Blanco as their big league catchers, with Conrad Schmidt in Triple-A Reno.
"Catcher is the one area that we probably lack some depth in, other than Conrad down below," general manager Kevin Towers said. "It's another guy that gives us protection in case there's an injury."
Tatum, who hit .245 with three doubles and seven RBIs in 31 games for Baltimore last season before being picked up by Houston, is out of Minor League options and would need to be placed on waivers again in order to be sent to the Minors.
"He's out of options, so it kind of gives us the spring to see what we have," Towers said.
The 28-year-old Tatum was selected by the Reds in the third round of the 2004 First-Year Player Draft and saw big league time with them in 2009. At the end of that season, he was claimed on waivers by the Orioles. The Astros claimed him on Oct. 28.
The D-backs had several good reports on Tatum and felt it was worth the gamble given their one remaining roster spot.
"[He's a] good catch-and-throw guy, and some people that knew him in the Baltimore system said some good things about him," Towers said. "He's good people, and he can hold his own behind the plate."
Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.