(SportsNetwork.com) - The start of a western road trip didn't go as planned for the Chicago Cubs, as they resume a three-game series Wednesday against the San Diego Padres at Petco Park.

The Cubs opened a six-game road swing against the Padres and Arizona Diamondbacks with Tuesday's 4-3 setback in southern California. San Diego scored two runs in the bottom of the eighth to go ahead for good.

Chris Coghlan's solo home run in the ninth inning -- his second of the evening -- wasn't enough for the Cubs, who have now dropped two straight since ripping off six straight wins. Dexter Fowler also went deep in a losing cause.

Cubs starting pitcher Jason Hammel was brilliant in the no-decision and gave up two unearned runs and three hits in seven innings. He struck out eight and did not walk a batter. James Russell allowed two runs (1 earned) for the loss.

"Jason could not have pitched better than he did tonight. It's impossible," Cubs manager Joe Maddon said. "He was outstanding. He kept getting better. He kept making pitches."

Tsuyoshi Wada was hampered by a groin injury to start the season and will make his season debut for Chicago Wednesday. Wada, a left-hander, went 4-4 with a 3.25 earned run average in 13 starts last season and lost his only start against the Padres, charged with five runs and five hits in four innings.

The Padres ended a three-game slide versus the Cubs and were led by Derek Norris' two-run double in the bottom of the eighth inning. Will Venable delivered an RBI single in the seventh inning, as the Padres won for the third time in the past eight tries.

Venable had been 1-for-19 against Hammel before his big hit.

"His slider is pretty vertical. I can remember offering at that in the past ... a lot. That was a trouble pitch for me. Tonight, he saved them for that last at-bat and threw me three of them," Venable said.

James Shields was aiming for win No. 6, but settled with the no-decision. He tossed seven innings of two-run ball and struck out 11 with only one walk.

"He pitched great. His stuff was good," Padres manager Bud Black said. "11 strikeouts tonight. Nice mix of pitches, spotting the ball."

Black hands the ball to Tyson Ross Wednesday and he is 2-3 with a 3.94 earned run average in eight starts. Ross was 0-3 in five outings until stopping the slide in last Thursday's 8-3 win against Washington, tossing five innings of two-run ball with six K's and three walks.

Ross has given up two runs in each of his past three trips to the mound and owns a 2-1 mark in three home starts. In three career meetings (2 starts) with the Cubs, the right-handed Ross is 1-0 with a 2.63 ERA.

San Diego won two of three games at Wrigley Field in late April.