Ortiz was hit hard in Thursday's 12-3 loss to the Cubs at Wrigley Field, giving up nine runs and nine hits in 2 1/3 innings to fall to 3-6. He was 0-5 in his last 10 starts, including 0-3 with a 12.23 ERA in five starts in July. He can clear waivers Monday and sign with another team.
Houston called up right-hander Sammy Gervacio from Triple-A Round Rock, and he will join the team Friday in St. Louis.
"At this point of the year, playing teams like this, they don't need to send anybody out there they feel like is not going to get the job done," Ortiz said. "I told them I understand. This is an important time of the year, and they have a couple of young guys that can throw the ball well.
"I don't know what they're going to do, but they didn't obviously feel like they can keep sending me out. I don't want to pitch like this and not have them confident in me. Even though I never wanted this to happen, it's part of the game."
Ortiz, 35, made the team as a non-roster invitee to Spring Training and split time between the bullpen and rotation before being moved into the rotation full-time on June 11. He was 1-1 with a 1.91 ERA in seven June appearances (four starts).
But Ortiz was rocked in a 9-0 loss at San Francisco on July 4 and never recovered. He chastised manager Cecil Cooper for pulling him out of his next start on July 9 against Washington after only three innings, but the two appeared publicly to have worked things out.
Ortiz gave up six runs and five hits in 4 1/3 innings Saturday against the Mets before falling apart Thursday at Wrigley Field. The poor outing put further strain on an Astros bullpen that pitched 17 innings in the final three games of the Cubs series, more than twice the amount of the innings the starters pitched (eight).
"What we've asked a couple of these guys to do is to get deep enough into the game to take advantage of our bullpen and give us a chance," Houston general manager Ed Wade said. "Unfortunately, not knowing from start to start whether Russ was going to get us deep enough was just overtaxing our bullpen.
"The side effect of these types of things is it just doesn't affect us that particular day, it affects us for days and beyond. You run a guy out there for multiple innings and you're asking him to bounce back and cover an inning or two the next day. It becomes an almost impossible situation to not only cover early exits by that particular starter, but then you cover innings going forward in subsequent games."
Gervacio, who has never appeared in a Major League game, is a side-arming right-hander who was 2-2 with a 5.40 ERA in 35 relief appearances at Round Rock.
"He's probably an early bullpen guy for us," Wade said. "Whether he can give us multiple innings or not remains to be seen. He's a different arm-angle guy, a little three-quarter, sidearm, a different look, particularly to left-handed hitters."
Wade said Bud Norris, who made his Major League debut in relief Wednesday, would take Ortiz's spot in the rotation, but Norris could still start Sunday in place of Roy Oswalt, who left Tuesday's game with a back strain and had a pain-killing injection Wednesday.
"So there are a lot of moving parts, and they'll be dictated by how Roy feels once he gets to St. Louis tomorrow," Wade said.
Ortiz won 67 games for the Giants between 1998 and 2002, helping them reach the World Series in 2002. He had his best season with Atlanta in 2003, when he won 21 games, but he was plagued by arm problems for much of the next few seasons and missed all of 2008 before signing with Houston.
"These guys have been awesome here in the clubhouse, and I appreciate Coop for putting me in there and [pitching coach] Dewey [Robinson] for helping and all the coaches and everything," Ortiz said. "This team has a very good chance of going to the playoffs, and they had to make a move to help that, not hurt it."
Ortiz believes he can still pitch in the Majors.
"It just depends on whether teams think so, too," he said. "Physically, I feel great and mentally I feel great, and the one thing about this is you can't do it forever, so we'll see. If no one picks me up, we'll go from there."
Brian McTaggart is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.