OAKLAND -- The funk that enveloped the Cubs through the end of June and early July continues to feel more like a distant memory, as does the A's postseason run with Jon Lester just two seasons ago.
Lester, making his return to the Coliseum for the first time since spending two months with Oakland in 2014, allowed two runs over seven innings, and Jorge Soler hit a three-run homer as the Cubs pounded A's starter Dillon Overton en route to a 7-2 win, their fifth straight.
"Any time you've been on the home side and come back as a visitor, it's different," Lester said. "There aren't many guys left from when I was there. It makes it hard to form a game plan."
• Lester shines in return to Oakland
Chicago is now 15-6 over its last 21 games, a swift reversal from its 5-15 record between June 29 and July 10, and own the Majors' best record at 67-41.
The A's, meanwhile, are 13 games below .500 (48-61), tying a season high for the sixth time.
Overton gave up seven runs on nine hits and was removed after three innings. His struggles with the long ball didn't take long to resurface, either, as Dexter Fowler led off the game with a homer and Soler's three-run shot came in the same inning as the Cubs staked Lester to a 4-0 lead.
"Believe it or not, I was actually hitting my spots better tonight," Overton said. "They just hit everything I threw."
It was more than enough for Lester, who retired 14 of the first 15 batters he faced before Brett Eibner homered to lead off a two-run sixth. The lefty struck out eight and improved to 12-4 with a 2.93 ERA.
"He pitched extremely well," Cubs manager Joe Maddon said. "He had a little bump there but he settled back in. That was impressive."
Lester wasn't the only former A's player to make an impact. Addison Russell, drafted by Oakland 11th overall in 2012, reached base three times and turned in an impressive backhanded defensive play in the fifth inning. Ben Zobrist, who played half of last season with the A's, made a remarkable play at second base to tag Khris Davis out on a steal attempt in the second inning.
MOMENTS THAT MATTERED
Soler-powered first inning: In his first at-bat after two months on the disabled list with a left hamstring strain, Soler belted a three-run homer to help the Cubs open a 4-0 lead before Lester threw a pitch.
"I just wanted to put a good swing on the ball," Soler said. "I was happy to be called up and I came ready." More >

Overton's woes continue: Overton entered Friday's game having allowed the most runs (19) and hits (34) of any pitcher in A's history over his first four starts, and his fifth only got worse. The Cubs were locked in early, rifling several sharp liners to left field, including the pair of first-inning homers, and Overton needed 84 pitches to get through three innings. Friday's start was the third time the lefty has been unable to finish more than 3 1/3 innings, and he's allowed 11 homers in his first 21 1/3 innings, seeing his ERA rise to 10.97.
"You know, I was telling my parents after my last outing: For a rookie, I might've given up the most home runs through four and five starts," Overton said. "It's a crappy feeling. You don't want to do that. I'm still adjusting to this league."

A run in with Fowler: Fowler went 2-for-5 and scored a run for the seventh straight game, his longest such streak in four years. The Cubs are 21-4 when he reaches base safely at least twice.

Eibner homers in debut: Eibner briefly jolted the Coliseum to life in his A's debut, opening the sixth inning with a homer just hours after being recalled from Triple-A Nashville. Eibner, who was acquired from the Royals July 30 in exchange for Billy Burns, hit .231 with three homers in 26 games with Kansas City this season.
"We can see what we like in him," A's manager Bob Melvin said. "The power is probably his biggest tool, as far as offensively." More >

QUOTABLE
"Sometimes a guy just has to show up and he gets the adrenaline going." -- Maddon on Soler's first-inning home run
SOUND SMART WITH YOUR FRIENDS
Overton is the first pitcher since at least 1913 to allow more than nine homers over the first five games of his career.
WHAT'S NEXT
Cubs:Jake Arrieta (12-5, 2.75 ERA), having lost three straight decisions, takes the mound against the Oakland Athletics for Saturday's 3:05 p.m. CT contest at the Coliseum. The Cubs have lost the last five games the right-hander has started, and he is winless against the A's in three career games (two starts), though Arrieta's last appearance against them was in 2012 while with the Baltimore Orioles.
A's:Sonny Gray (5-10, 5.84 ERA) starts the 1:05 p.m. PT contest for Oakland, hoping to put Sunday's setback against the Indians behind him. Gray allowed seven runs in three innings in that one. It was the second time in three starts he allowed seven runs, and he has the highest ERA among qualifying starters in the Majors. The righty has never faced the Cubs.
Watch every out-of-market regular-season game live on MLB.TV.