Tyson Ross has allowed two earned runs in his last three starts and four of his last five. His ERA in May is 3.00. The Padres have won two of his last three starts and were shut out in the loss. Ross hasn't allowed a home run in May and has allowed 17 hits in 18 innings with 17 strikeouts.
James Shields allowed one run on six innings in his most recent start in Seattle. Despite a 3.91 ERA, Shields has a 5-0 record. And Andrew Cashner has allowed two earned runs or fewer in five of his eight starts this season.
But back-to-back bumpy starts by Odrisamer Despaigne and Ian Kennedy have crippled any hopes of the Padres gaining momentum.
After allowing one walk and no hits with six strikeouts through four innings Sunday, Kennedy allowed six runs on three hits and three walks in a span of nine hitters. Over his last two starts, Kennedy has allowed 11 runs on 11 hits and seven walks in 9 2/3 innings.
Despaigne, who is in the rotation because right-hander Brandon Morrow is on the disabled list with shoulder inflammation, has allowed 15 runs on 20 hits and three walks in eight innings over his last two innings.
One of the main reasons why the Padres are 19-20 is that they've yet to go through a complete turn of the rotation without at least one starting pitcher having a bad outing.
The Padres' team ERA soared to 4.43 Sunday after the Nationals hit a pair of three-run homers in a 10-5 rout. Last season, the Padres had the worst offense in the Major Leagues. But the pitchers had a staff ERA of 3.27. That was the fourth-best mark in the Major Leagues and the second-best in the National League.
Padres manager Bud Black says both the Padres' pitching and offense have been on a Jekyll-and-Hyde roller coaster this season.
The Padres have scored 175 runs, the third-highest total in the NL. But they have also been shut out six times. They have scored eight or more runs seven times, but they have scored one or zero 10 times.
On the flip side, they have given up more than 10 runs six times, including for the third time in six games Sunday.
"We're not having many 3-2 and 4-3 games," said Black. "It's been a lot of feast or famine."
From the scorebook
• Left fielder Justin Upton had his second two-homer game of the season Sunday and the ninth multihomer game of his career. He now has four multihomer games at Petco Park, which is tied with Adrian Gonzalez for the highest total in Petco Park history. Two of those multihomer games at Petco Park were as a member of the Padres this season and two came as a visitor. Upton has eight homers in 72 at-bats at Petco Park this season. The single-season record for home runs at Petco Park is 15, set by Will Venable in 2013. Upton was 3-for-3 Sunday and is hitting .375 (27-for-72) at Petco Park this season with 20 RBIs.
• Second baseman Jedd Gyorko hit his second homer of the season Sunday. Gyorko is 13-for-37 (.351) with four doubles and two homers and six RBIs in 14 games this month after entering May with a .135 batting average.
• Right fielder Matt Kemp was 2-for-4 Sunday. It was his 12th multihit game of the season and the second over the past four games against the Nationals. Kemp was 5-for-14 against the Nationals after going 4-for-37 during the Padres' nine-game road trip before the Washington series.
• Infielder Cory Spangenberg was 0-for-4 with three strikeouts Sunday and is hitless in 13 straight at-bats with eight strikeouts.