WASHINGTON (AP) — If second base were located somewhere on the fringe of the outfield grass behind the shortstop, Jeff Baker’s throw would have been on target.

The Chicago Cubs wish they could invoke lots of similar “ifs” this season. Instead, they had to come up with another way to explain a loss, with Baker front and center after his first-inning miscue in Tuesday night’s 3-2 defeat against the Washington Nationals.

Baker was only 30 feet or so from second when he fielded a routine grounder with the bases loaded and none out, but his throw sailed more than 10 feet wide of the bag and into left field. Instead of allowing one run on a double play, the Cubs were in a 2-0 hole that became 3-0 on Wilson Ramos’ infield single.

“When I pivoted, my back foot slipped out and my lower back started to spasm up a little bit,” said Baker, who left the game in the third inning with back spasms. “That’s frustrating. … It should have been a double play. I didn’t make the play.”

Baker was in the starting lineup to give All-Star shortstop Starlin Castro a rest.

The three-run first was just enough of a cushion for a Nationals cadre of pitchers that included Ross Detwiler (1-0), recalled from Triple-A before the game because Washington needed an extra starter due to a recent doubleheader. Detwiler, making his season debut, took a shutout into the sixth and was removed after giving up Aramis Ramirez’s two-run homer.

“We’ve got to figure out ways to win,” Chicago outfielder Marlon Byrd said. “We can’t think back and go, `Oh, we didn’t win because of this.’ We have to figure out ways to win, and we’re not.”

Detwiler allowed four hits over 5 1-3 innings with one strikeout and no walks. The Cubs were stymied the rest of the way by Todd Coffey, Sean Burnett, Tyler Clippard and Drew Storen (21st save) as the Nationals improved to 4-5 under manager Davey Johnson.

The Nationals are back over the .500 mark thanks to their sudden knack for winning one-run games. Each of Washington’s last nine wins has come by one run or in extra innings, and the club is 12-3 in one-run games since June 1.

“I love one-run wins, believe me,” Johnson said. “But every decision you make in one-run ballgames is kind of critical. Once in a while I’d like to have a laugher.”

Chicago’s pitcher was also making his 2011 debut. Ramon Ortiz (0-1) had the rough first inning — exacerbated by Baker’s miscue — but he settled down and didn’t allow another run. He went six innings, gave up seven hits and struck out seven in his first major league start since May 19, 2010, for the Los Angeles Dodgers.

Ortiz’s contract was purchased from Triple-A before the game, the latest move in a season-long pitching carousel for the Cubs. Ortiz became the 10th Chicago starter this season, his services needed because Carlos Zambrano is on the disabled list with a sore back. Four of Chicago’s five starters from the opening day rotation have been on the DL this season.

With all that going on, manager Mike Quade had a ready-made answer when asked about Baker’s back spasms.

“Day-to-day,” Quade said, “which has become my middle name.”

NOTES: Ortiz became the Cubs’ second fill-in starter in two days. Casey Coleman started Monday because Ryan Dempster was recovering from a stiff lower back. … Chicago also placed reliever Marcos Mateo on the 15-day disabled list with a sore elbow. Mateo was flown to Chicago and had an MRI on Tuesday, but the team doesn’t expect to have the results for another day or two. … The Cubs flip-flopped a move they made Monday, recalling reliever Chris Carpenter from Iowa and optioning Coleman to the Triple-A club. … First lady Michelle Obama was cheered as she took part in a pregame ceremony honoring children of military families. She watched from the infield as a boy from a military family threw the ceremonial first pitch to Nationals 2B Danny Espinosa. Mrs. Obama then gave Espinosa a hug.

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