PHOENIX - If their offense doesn't come around rather quickly, the Diamondbacks could find themselves in worse position than just second place in the National League West.

After sitting in first place for 66 days, they finally lost their lead in the division, thanks to a 4-2 loss Monday night to the visiting Chicago Cubs that was coupled with yet another victory by the surging Los Angeles Dodgers.

The Dodgers (51-47) beat Toronto 14-5 and hold a half-game lead over the D-backs (51-48), who had held or shared the top spot since May 15.

"There's a long way left to go in the season, but it is a loss," Arizona manager Kirk Gibson said. "I don't think you change the way you're doing things. We're trying to play good ball. We're trying to make good plays. We're trying to swing the bat and pitch as good as we can.

"There's a long way to go. This doesn't mean we're out of it by any means."

Arizona's offense, though, has gone completely stagnant. The D-backs, losers of four of their past five, are hitting .194 (69 for 355) in their past 10 games and .143 (6 for 42) with runners in scoring position in their past seven games.

Monday, they managed just six hits off six Cubs pitchers, including emergency starter Chris Rusin (1-0), who took Matt Garza's scheduled start after Garza was traded earlier Monday to the Texas Rangers for five minor league prospects.

The Cubs got a solo home run from catcher Dioner Navarro and a two-run shot from rookie center fielder Junior Lake, who went 4 for 5 and also drove in an insurance run in the ninth.

Martin Prado hit a run-scoring sacrifice fly and Paul Goldschmidt delivered an RBI single up the middle for both of Arizona's runs in the sixth.

"That's baseball for us right now," outfielder Gerardo Parra said. "We're not hitting right now and not everybody is doing good. But tomorrow's another day so let's continue to play hard and let's continue to try and win."

Prado said there is no panic creeping through the D-backs' clubhouse, even though the club finally lost its grip on first place.

"No, no, no. Not at all," he said. "There's nothing like that going on here. All we're thinking about it coming out and playing hard, coming out and thinking about winning."

Lake's two-run homer off Tyler Skaggs with no outs in the fifth inning gave the Cubs a 3-0 lead. Lake's RBI single in the ninth scored Darwin Barney with an insurance run.

Skaggs (2-2) took the loss for the Diamondbacks. Kevin Gregg pitched the ninth for his 19th save.

Rusin appears to be the Cubs' go-to pitcher after trades. When Scott Feldman was dealt to Baltimore, Rusin stepped in, but did not receive a decision in an eventual 8-7 loss to Oakland.

After Navarro's solo blast gave the Cubs an early 1-0 lead in the second, Chicago added a pair in the fifth as Lake slammed a 2-0 pitch into the left-centerfield bleachers with Rusin on base.

Effective from the start, Rusin - 8-7 at Triple A Iowa - retired the first seven he faced. With one out in the third, Didi Gregarious slapped a single to right but was stranded when Skaggs struck out and A.J. Pollock fouled out to the catcher.

Through the first five innings, Rusin allowed two baserunners.

Rusin walked Cody Ross with one out in the fifth, but Ross was doubled up when right fielder Cole Gillespie grabbed Parra's sinking liner and fired to first baseman Anthony Rizzo for the double play.

Rusin pitched into the sixth and left with runners on first and second and no outs.

In that inning, the Diamondbacks managed to score both runners. First, Prado's sacrifice fly scored Gregorius, and Goldschmidt drove in his 79th run of the season with an infield single.

The Diamondbacks had an opportunity to take the lead, but could not capitalize in the seventh as pinch-hitter Eric Chavez flied to center field with the bases loaded and two outs.

In the eighth and with the tying run at third with two outs, Miguel Montero struck out to end that threat.

Earlier, plate umpire Doug Eddings made sure things did not get out of control. With a history of Arizona suspensions this season for hit batters, Eddings directly addressed the issue in the Cubs' half of the fourth inning. With two outs, Skaggs hit Navarro on the right knee with a pitch. Immediately after Navarro was hit, Eddings pointed to Skaggs and then pointed to both the Diamondbacks and Cubs dugouts.


• Who: Cubs at Diamondbacks

• When: 6:40 p.m.

• TV; radio: FSAZ; 1490-AM

Contributing: The Associated Press