CHICAGO -- The Cubs went through the first three weeks of their schedule without losing consecutive games. Chicago's pitching staff rolled, the lineup poured out runs and the defense was stellar in pushing the club to the National League's best record.

Really, the Cubs had not been tested too much throughout that run, but that impressive streak ended with a 6-5, 10-inning loss to the Brewers on Saturday afternoon. For the first time this year, the North Siders lost in back-to-back games, and both one-run losses at that.

• Box score

"These last two games were pretty stressful for them to win," said Steven Souza Jr., who launched a game-tying homer in the eighth inning on Saturday. "Good or bad or indifferent, we're just trying to move on and focus on the game at hand, especially with such a short season. You can't dwell on any wins or losses."

Here are three takeaways from Saturday's defeat, which dropped Chicago's record to 13-5 on the campaign.

1) The Jeffress effect
The Cubs have been winning, even as manager David Ross has tried to sort through different relief combinations. Closer Craig Kimbrel has been searching for his prior form and the group overall entered Saturday with a 6.10 ERA (13th in the National League).

Signed to a one-year deal over the offseason, righty Jeremy Jeffress has been a stabilizing force for the group.

"J.J.'s been phenomenal," Ross said recently. "Every scenario I've put him in, he's risen to the occasion."

Jeffress entered Saturday with no hits or runs allowed through seven innings, and had a 1.03 win probability added (first among NL relievers). He built on that showing by facing the minimum in the ninth, when he set down Omar Narváez, Keston Hiura and Christian Yelich in order to preserve a 4-4 deadlock.

It took 2020's new extra-innings rules for Jeffress to finally flinch. He allowed a run-scoring double to Avisaíl García and later gave up back-to-back, two-out singles. The second in that sequence from Luis Urías was an infield hit that scored García to give Milwaukee a 6-4 lead.

Jeffress' season line now includes one earned run, but that does not take away from what he has meant for the Cubs to date.

"The things you guys don't see," Ross said, "he's been a leader in the bullpen for some young guys finding their way. ... All around for J.J., I mean, he's been a phenomenal addition to our group. It's another guy that we lean heavy on and he's answered the bell."

2) Rea earning trust
When the Cubs were forced to scratch Tyler Chatwood (mid-back tightness) from his start on Friday night, that initiated a chain reaction within the rotation. Alec Mills moved up to Friday's outing and a vacancy opened up for righty Colin Rea to take the ball Saturday.

"I was happy to get that call," Rea said. "I'm just kind of willing to fill in wherever I need to."

Rea moved out of the Cubs' bullpen and worked 3 1/3 innings in his first Major League start since July 30, 2016. The right-hander pitched to contact, generating six ground balls and allowing just one hit to the first 10 batters he faced through three innings.

Helped by some seeing-eye hits, the Brewers struck for three runs in the fourth, chasing Rea from the game. Still, the pitcher has started to work his way into Ross' favor, especially when it comes to the Cubs identifying a sixth starter.

José Quintana is on the 10-day injured list and is still working his way back from a left thumb injury. At the South Bend (Ind.) alternate training site, the Cubs have arms like Adbert Alzolay, Tyson Miller and Justin Steele, among others. Chicago also has doubleheaders looming this Monday and Wednesday, as well as on Aug. 29 and Sept. 5.

"Colin gives us that [depth]," Ross said. "We've got some guys at South Bend when we need to call on them, and some depth down there."

3) Waiting on Bryant, Báez
Anthony Rizzo collected three hits, including a first-inning homer and a run-scoring double on Saturday. The hot-hitting Ian Happ churned out a pair of doubles, including one to bring in a run. Souza had his big home run, too.

What the Cubs lacked again on Saturday was much from Kris Bryant (1-for-5 in his return from a left wrist issue) and Javier Báez (0-for-5 with two strikeouts). Bryant (89 wRC+) and Báez (63 wRC+) have each been in season-opening slumps.

In such an abbreviated season, stats over 18 games are important, but still need to be viewed through the small-sample-size prism. So, do not expect Ross to overreact to any underwhelming slash lines when it comes to the mainstays atop his lineup.

"I trust in the players that have the track record," Ross said. "We're going to have good days and bad days. I'm not panicked. I'm not worried. ... I don't worry about the big boys that have the resumes. They're our horses. We ride them, and through the good and the bad."