CHICAGO -- Coming into this season, the Nationals' relief corps was considered the strength of the team because it had right-handers such as Chad Cordero, Jon Rauch and Luis Ayala at the back end of the 'pen.

Not anymore.

Cordero is out for the season because of shoulder surgery, and Rauch and Ayala were traded recently for young position players. General manager Jim Bowden acknowledged on Sunday that the Nationals have to start from scratch in order to get production out of the bullpen.

Entering Tuesday's action against the Dodgers, the Nationals relievers rank 21st in the Major Leagues in ERA [4.26], have walked 201 batters and given up 45 home runs.

At the moment, only Joel Hanrahan and Saul Rivera are guaranteed to have a job out of the bullpen next year. Hanrahan will be the closer, while Rivera will be one of the setup men. Cordero is not expected to be back with the team, according to sources.

"We have to completely rebuild the bullpen from scratch," Bowden said. "That's what we are doing. We are starting with Hanrahan. It's an adjustment period. It could be painful at times.

"We started with Cordero, Ayala, Rauch and Rivera. Those four were as solid as it comes. Except for Rivera, the other three are gone by injury or trade, and we have to rebuild it, and it's not easy."

The Nationals have already called up some of their starters from the Minor Leagues to see if they could be quality relievers. Right-handers Garrett Mock and Marco Estrada are two guys who have been given relief roles, and they have been mediocre, at best.

Bowden said more starting pitchers from the Minor Leagues will try out for relief roles. He declined to mention names, but one baseball source said the team is considering calling up left-hander Michael Hinckley, who was once the top pitching prospect in the Expos' system.

By the time the team moved to Washington, injuries and lack of control kept him from reaching the big leagues. Finally healthy, Hinckley was able to get the velocity on his fastball back and is now a quality reliever out of the bullpen for Triple-A Columbus. He has been often clocked in the low 90s mph. Entering Sunday's action, Hinckley had a 2.95 ERA in 16 games for Columbus.

"We feel blessed we have a lot of good arms in the Minor Leagues," Bowden said. "Some we are going to see in September. Some we are going to see in Spring Training. So our work is cut out for us."

Pitching matchup
WSH: RHP Collin Balester (2-6, 4.99 ERA)
Last Wednesday, Balester gave the Nationals six effective innings, giving up three earned runs, but Washington couldn't push a run across despite notching nine hits off Philadelphia starter Brett Myers. Balester is on a personal three-game losing streak.

LAD: RHP Derek Lowe (10-10, 3.89 ERA)
Lowe remains on a short leash. Once known as an innings eater, he was lifted with a 2-1 lead after issuing a one-out walk in the seventh inning against the Rockies, having thrown 107 pitches. He allowed four hits and struck out seven. He also has double figures in wins in seven consecutive seasons. Lowe went 8-1 two years ago after Greg Maddux was acquired and he's 1-0 this year with Maddux as a teammate.

Tidbits
The Nationals are 3-10 in rubber games, which decide a three-game series. ... The Nationals have eight rookies on the current 25-man roster -- Balester, Emilio Bonifacio, Estrada, Anderson Hernandez, John Lannan, Charlie Manning, Mock and Steven Shell. ... The Nationals/Expos have won 284 games against the Cubs since 1969.

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Up next
• Wednesday: Nationals (Tim Redding, 8-8, 4.54) vs. Dodgers (Greg Maddux, 6-10, 4.25), 7:10 p.m. ET
• Thursday: Nationals (John Lannan, 7-12, 3.95) vs. Dodgers (Clayton Kershaw, 2-4, 4.11), 7:10 p.m. ET
• Friday: Nationals (Odalis Perez, 5-10, 4.21) vs. Braves (TBD), 7:35 p.m. ET