CHICAGO -- The Cubs finally won a one-run game on Sunday, and it took nearly everyone on the roster to achieve it.

Daryle Ward hit a walk-off RBI single in the 10th inning to give the Cubs a 4-3 victory over the Washington Nationals for their first one-run victory and fifth win in a row.

"Earlier in the year, this type of game was eluding us," said Cubs manager Lou Piniella, "and now we're finding ways to win it."

Matt Murton doubled to open the 10th against Ryan Wagner (0-2) and, one out later, reached third on pinch-hitter Henry Blanco's single. Ward, who entered the game in the ninth as a pinch-hitter, then lofted a 2-1 pitch to left-center over the pulled-in outfielders to drive in the game-winning run.

"It's definitely a tough job," Ward said of coming off the bench. "I happen to be pretty good at it and pride myself on it, and I want to be the best at it. If it's pinch-hitting late in the game and [being] a spark plug for the rest of the team, than that's what I want to do -- and do it to the best of my ability."

With the Cubs trailing 3-2 in the ninth, Chad Cordero walked pinch-hitter Cliff Floyd, who was lifted for pinch-runner Jason Marquis. Ward advanced Marquis to second on a single to left, and, one out later, the pitcher-turned-runner scored on Ryan Theriot's single to tie the game at 3.

Theriot worked the count to 2-2 and then fouled off four pitches before connecting.

"I'm up there just battling," Theriot said. "I know everybody in this clubhouse wished they could have been in that spot and wanted to be in that spot, and I think that's what makes a team great. When we've got everybody in here dying to be up in a crucial situation -- and with so many capable guys -- it's a lot of fun."

Angel Guzman, recalled from Triple-A Iowa, didn't get a decision in his first start for the Cubs. The right-hander remained winless in 11 career starts.

Guzman did retire the first 10 batters he faced, and the only downside came in the fourth when the Nationals loaded the bases and Guzman walked Brian Schneider to bring in a run.

"The win was special, but Guzman really pitched well," Piniella said. "He went out there and gave us five good innings -- one-run ball, threw strikes, got his breaking ball over [the plate]. That was something that we can't overlook."

It was the Cubs' first one-run win after going 0-6 in such games so far this season, and they're now above .500 for the first time since April 7. The Cubs are 5-0 in May for the first time since 1937.

"Over the past week or so, we've won a lot of two-run ballgames, and now we've won a one-run ballgame, and to me, that's very important early in the season," Piniella said. "We've been winning good baseball games and winning close baseball games, which to me is much more important than winning by margins, because these are good confidence boosters for a baseball team."

Everybody played except for starting pitchers Carlos Zambrano, Rich Hill, and Ted Lilly and reliever Rocky Cherry, who was ready to pitch the 11th, if needed. Lilly would've gone to the pen if the game had gone any longer, Piniella said. Alfonso Soriano ended up at second base for the first time since Oct. 1, 2005.

"I'm not comfortable, but thank God, I didn't get one ground ball," Soriano said. "It's good to know [Piniella] can put me at any position."

"If we were playing seven or eight days in a row, we wouldn't have been able to do it this way," Piniella said. "Because of the day off on Monday, we can take some liberties and do the things that we did."

The last time Piniella made a gazillion double switches, he asked Cliff Floyd to help figure out who would play where defensively. On Sunday, Piniella asked Derrek Lee.

"And D-Lee was wrong," Floyd said, laughing.

"We're having fun," Ward said. "We're almost playing like Little League ball, but we're grown men."

The Cubs tied the game at 1 in the fourth on back-to-back doubles by Jacque Jones and Mark DeRosa. In the fifth, after the Cubs loaded the bases, Nationals pitcher Shawn Hill hit Jones to force in the go-ahead run.

Soriano and Lee each extended their hitting streaks as well as the number of consecutive games in which they've reached base safely. Soriano has a 15-game hitting streak, matching his career high, and has gotten on base in each of the 23 games he's played. Lee has reached base safely in all 29 Cubs games, and his single in the first extended his hitting streak to 14 games.

But the post-game congratulatory shaving-cream pie went to Ward, who picked up his first RBI of the season at just the right time.