Oakland was swept in three games at San Francisco to kick off the nine-game excursion and fell to 4-9 this month following Sunday's 6-2 loss against the Giants at AT&T Park. Jack Cust had a team-high three hits and both Kevin Kouzmanoff and Landon Powell knocked in a run for the A's, who received a rough outing from starter Vin Mazzaro.
Mazzaro allowed four runs -- three earned -- and six hits through six innings to suffer his first loss of the 2010 campaign (2-1).
"We had too many things go wrong in a three-game series to overcome," said Oakland manager Bob Geren.
Kouzmanoff is riding a 14-game hitting streak in which he owns three homers and 11 RBI. Oakland will also visit St. Louis on the trek and is four games off the lead in the American League West standings.
Trevor Cahill hopes to get the A's back into the win column when he makes his 10th start of the season tonight. Cahill is 4-0 with a 1.91 earned run average over his last five starts and defeated the LA Angels of Anaheim the previous time out on Thursday, as he tossed eight innings of one-run ball.
The Cubs will continue a nine-game homestand Tuesday and ended a three-game slide by salvaging the finale of a three-game set versus the crosstown-rival White Sox with a 1-0 win on Sunday behind a stellar performance by Ted Lilly.
Lilly did not allow a hit through eight innings and permitted a leadoff single to Juan Pierre in the ninth inning. Lilly struck out three batters in just his second win of the season and Carlos Marmol posted his 13th save despite walking a pair of hitters in a scoreless ninth inning.
"We're in a situation there where they're going to have a chance to tie it up," Lilly said. "How many times in those situations have we seen where Marmol walks a guy or falls behind in the count and then finds a way?"
Chad Tracy drove in the lone run of the game in the seventh inning for Chicago, which is 7 1/2 games off the lead in the NL Central.
Carlos Zambrano will try to build off his latest winning start when he takes the mound tonight. A recent demotion to the bullpen may have worked for Zambrano, who recently took the hill in a 9-4 win at Milwaukee last Wednesday and yielded three runs in five innings.
Zambrano is 2-4 with a 6.05 earned run average in 19 games -- six starts -- this season and will face Oakland for the second time in his career. The fiery right-hander beat the A's back on June 20, 2004 and held them to a run and five hits with eight K's in 6 2/3 innings of a 5-3 victory.
Chicago won two of three meetings with Oakland from June 18-20 of the 2004 campaign and is 93-100 against the American League. The Athletics own a solid 131-105 ledger in games played against the Senior Circuit.