WASHINGTON -- The Chicago Cubs threw eight straight shutout innings on Tuesday night and even that was not good enough for a victory.

A shaky first inning by 38-year-old starter Ramon Ortiz might have been limited to one run instead of three in the Cubs' 3-2 loss to the Washington Nationals if not for Jeff Baker's throwing error on a ground ball by Laynce Nix with the bases loaded.

Baker was injured on the play and left the game with lower back spasms in the third inning.

"Ortiz gave us a chance, he did a good job," Cubs manager Mike Quade said. "It was an unfortunate first inning. After that we just couldn't find a way to score."

Losing players to injury has become a daily situation for Quade and the Cubs.

"He slipped on the Nix ground ball," Quade said of Baker. "He may miss a couple of days. Day to day. It's become my middle name."

Quade has lost pitchers Carlos Zambrano, Marcos Mateo and possibly Ryan Dempster since Thursday.

Ortiz, who signed a minor league contract April 2 and has been pitching for Triple-A Iowa, pitched well in spite of the three runs scoring, allowing seven hits over six innings while striking out seven and walking three.

"I threw a good fastball, slider and changeup then. Now I have to pitch," Ortiz said. "I'm 38. I don't have 97 or 98 [mph] anymore. I have to hit the corners."

Ortiz, who signed a split major league and minor contract for $900,000, hopes to continue to pitch in the rotation for now.

"I'm very happy," Ortiz said. "I worked hard for this opportunity. Now I am here, I have to keep throwing the ball well."

As for Baker, he is hoping that sa few days of rehab on his back will allow him to return to the lineup.

"I slipped on that double play ball. My back foot went out and my back started to spasm," Baker said. "Then it locked up my whole back. It [stinks]. It's one of those things. You want to grind through it but at the same time if you push it you're going to be out for a couple of weeks."

The frustration of not getting the job done is obvious to Baker and his teammates who are now a season-worst 17 games under .500.

"I think under the circumstances everybody is upbeat and as positive as they can be," Baker said. "It stinks. Guys are frustrated. You want to get better, you want to win. Like I said, it's not a lack of effort or preparation. We are just not executing, and we're getting out-executed."

Third baseman Aramis Ramirez's two-run homer in the sixth was his eighth home run 13 games and accounted for the Cubs' only runs.

"Seems like everything is going against us," Ramirez said. "But we need our pitchers to be healthy. Hopefully Zambrano and Dempster won't be out too long. We need them to be healthy in the second half."