Workman, who had worked his way into the rotation, was sent to Triple-A Pawtucket after the Red Sox acquired Jake Peavy on Wednesday. Workman was in Buffalo with the PawSox when he received word to join the Red Sox in Houston.
"It's obviously great to be back up here," said Workman, who is ranked the club's No. 11 prospect. "I didn't expect to be back up now. I couldn't be more excited about it."
Nava will rejoin the Red Sox on Thursday in Kansas City.
"I'm not sure [of my role]," Workman said. "I just want to pitch well whenever they give me the ball, whatever role I'm in."
Workman, who will turn 25 next Tuesday, grew up in Bowie, Texas, near Wichita Falls, and played in college at the University of Texas.
"I'm definitely excited to come back home, or close to home," he said. "I have some buddies from school coming over for the next couple of days and my family's coming down."
Workman was 1-1 with a 3.54 ERA for the Red Sox in four games this season, three of them starts since being called up July 9.
"He's been impressive," manager John Farrell said. "When we asked him to make three starts, he was very effective."
Workman will work out of the bullpen, for now.
"We need contributions out of the bullpen," Farrell said. "I don't say he's solely a long guy, because we've had other young pitchers come up and been thrust into pretty high level situations, depending on availability on a given day."
Gene Duffey is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.