While Patrick Corbin has enjoyed a breakout campaign in 2013, he's fallen off the pace down the stretch.
Stephen Strasburg has been steady all season, but he doesn't have much to show for it.
Leading the team in wins, innings pitched (203 1-3) and strikeouts (171), Corbin (14-7, 3.28 ERA) has emerged as the Diamondbacks' ace in his first full season in the majors. The left-hander, who was named to the NL All-Star team, tied the franchise record for consecutive wins to open a season by going 9-0 with a 2.06 ERA in his first 11 starts.
Corbin, though, has since gone 5-7 with a 3.98 ERA, including 1-4 with a 7.84 ERA in his last six outings.
"He just doesn't have a lot of life on his pitches right now," manager Kirk Gibson told MLB's official website.
After allowing six runs over two-plus innings in the shortest start of his career Sept. 17 in a 9-3 defeat to the Los Angeles Dodgers, Corbin surrendered four runs and a career-high 10 hits in 4 1-3 innings Sunday in a 13-9 win at Colorado.
"I left some breaking balls up today, I thought it was my worst all year," he said. "My slider is not as sharp right now. I know that and I'm just not as consistent with it. I don't know why."
Corbin is 1-0 with a 2.57 ERA in two starts versus Washington (84-75). He yielded two runs in seven innings opposite Strasburg in a 3-2, 11-inning road win June 27.
After getting shut down early last season, Strasburg (7-9, 3.02) has struck out 187 over a career-high 176 innings while posting a .206 opponents' batting average, among the lowest marks in baseball.
Despite those numbers, Strasburg will head into the offseason with a losing record. The Nationals have provided him with a combined 11 runs of support in his defeats, though.
"I think for me, there's a lot of things that I've learned this year," he said. "A lot of improvements to be made. And I'm going to work harder than I did the last offseason, and that's all you can really do."
Strasburg, 2-0 in his last eight outings, gave up three runs over six innings in a 5-4 walkoff win over Miami in the back end of Sunday's doubleheader. He struck out six to become the third-fastest player to 500, doing so in 426 1-3 innings. Only former Cubs' starters Kerry Wood (404 2-3 innings) and Mark Prior (421 2-3) were quicker.
Strasburg is 1-0 with a 2.00 ERA in three starts versus Arizona (80-79), which just dropped three of four at San Diego by a combined 20-7 score. Martin Prado hit a two-run homer in Thursday's 3-2, 11-inning defeat.
Paul Goldschmidt singled and scored, extending his hitting streak to 16 games. The first baseman, batting .406 with five homers and 17 RBIs during that stretch, is hitting .395 with a homer and nine RBIs in his last 10 games versus Washington.
The Nationals are hoping to avoid losing four straight for the first time since Aug. 4-7 after getting swept at St. Louis this week. Washington managed one run in the final two games of that set, falling 4-1 in Wednesday's finale.
"There's pride that comes into it when you play these games," manager Davey Johnson said. "This club is used to being a spoiler but we didn't play that well."
Washington has taken six of eight from Arizona.