MIAMI -- It's the last thing the Chicago Cubs need right now. Fighting through injuries and a long road trip, if the most important -- and up until now most reliable -- part of their game goes south, they could really be in trouble.

Cubs starters had been on such a roll this season, but on Saturday, there was no doubting what John Lackey did on the mound. Staked to a 4-1 lead over the Miami Marlins, he wasn't very good.

"John did not have his best day," manager Joe Maddon said after the 9-6 defeat. "That's what it came down to. Normally when we score that many runs, we're going to win a baseball game."

In fact, when the Cubs had scored four or more runs -- let alone six -- they were 44-3 this season. Make that 44-4 after Lackey gave up the lead during a four-run fifth inning. In total, he gave up seven runs and made some poorly located pitches.

It wasn't all Lackey's fault, though. A one-out ground ball by the still-speedy Ichiro Suzuki resulted in an infield hit in the fifth inning, when shortstop Addison Russell rushed his throw, which bounced past Anthony Rizzo. Ichiro advanced to second and the floodgates opened. A 4-3 Cubs lead turned into a 7-4 deficit.

"I have to be better than that. Four runs needs to be enough to win that game," Lackey said. "I don't know what planet that's a hit on by the way (in reference to Ichiro)."

It's the second night in a row Russell has made a key error that led to runs being scored. On Friday, Kyle Hendricks gave up four on a grand slam after a Russell error, and though they were unearned, they still count. Cubs starters had gone 23 consecutive games without giving up more than three runs, but in three of their past five starts, they've gone over three, all resulting in losses.

After starting pitching, the next-most reliable thing about the Cubs this season has been their defense. It's showing cracks this month, and Russell might be a concern. Every shortstop is going to make mistakes -- the position is just so demanding -- but the routine errors are starting to pile up. Most have come via his arm.

"I feel like my footwork is fine," Russell said. "My arm is fine. Maybe just getting around the ball or getting too inside the ball on throws. Just have to [wear] it."

Though fielding percentage never tells the whole story, in this case it might be applicable due to the routine nature of the miscues. Russell has nine errors so far, tied with several others for second most in the National League. His .966 fielding percentage is second to last because he has the 11th-most chances for a putout among shortstops. Think about it: Russell has the second-most errors and only three regular shortstops have had fewer chances (Atlanta's shortstops have split time).

"I need to do a better job cutting down the errors," Russell said. "They're going to capitalize. They did two nights in a row."

Added Maddon: "They are plays Addy normally makes. He has to get there in a hurry, but those are plays he definitely makes.

"You can't give teams extra outs, but we did."

It's not all on Russell, though. Rizzo hasn't been scooping balls as well lately -- Maddon blamed the first baseman's bad back on one play earlier in the week -- and he threw one away in the seventh, trying to lead his pitcher at first base. It led to more runs. According to ESPN Stats & Information research, the Cubs have steadily declined on defense from April to June. So if they can't rely on starting pitching and defense, what can they rely on while dealing with the walking wounded?

"It's the same mood," Russell said of the locker room. "There are younger ballplayers playing. We're playing aggressive. I like the style we're playing. Sometimes bad things [happen] and it just snowballs from there."