CHICAGO -- In the hours leading up to Sunday's game against the Giants, Cubs manager David Ross called it a great test for rookie Justin Steele. As the lefty continues to learn his way as a big league starter, San Francisco presented a daunting task.

Steele fought his command, but he made his way through a five-inning learning experience in a 6-5 loss to the 93-win Giants at Wrigley Field. The defeat completed a series sweep of the North Siders.

"It's a good ballclub," Steele said. "They have the best record in baseball for a reason. It still doesn't take away from the fact that I need to execute pitches more often, make better pitches."

Here are three takeaways from Sunday's loss:

1) Pros and cons for Steele
There were good moments for Steele -- such as consecutive strikeouts of Buster Posey and Evan Longoria, for example, to limit the damage to one run in the third inning.

And there were more growing pains -- such as Wilmer Flores' two-out, two-run homer in the fifth that swung the momentum in San Francisco's favor for good.

"We're in that game before that home run," said Ross, who noted that Steele's fastball command was the primary culprit in this outing.

In his sixth start for the Cubs, Steele built up to 101 pitches. That marked a career high in the Majors and his most in a professional game since June 4, 2017 (103 for then-Class A Advanced Myrtle Beach). The lefty struck out four, walked two and allowed five runs on 11 hits.

Steele said his biggest takeaway from this start was the importance of getting ahead quickly. That proved difficult against an all-righty lineup and with both his four-seamer and sinker defying his will.

"I felt good with both breaking balls," Steele said. "Moving forward, it's just fastball command and getting that strike one, is my main focus."

2) Happ keeps foot on gas
Over the past week-plus, while Ross was self-isolating away from the team following a positive COVID-19 test, he enjoyed watching Ian Happ's plate appearances from a different perspective.

What Ross saw was a batter hunting pitches, rather than one waiting for something specific.

"Just talking to him and knowing him for a while," Ross said, "he really values his on-base and taking walks. And you can get to a space where, do you try to find the perfect pitch and swing at every strike?

"I think the mentality that most hitting coaches will tell you is like, 'Swing, swing, swing, and then shut it down,' rather than maybe the opposite. I just see a guy that, his bat’s in the zone a long time, he's using all fields.

"He's in rhythm. He's aggressive right out of the chute. Not trying to size anything up."

In the finale against the Giants, Happ attacked an 0-1 slider in the zone from Logan Webb and connected for a solo homer to center. It marked the outfielder's 22nd shot of the season and his eighth in his past 16 games.

Back on Aug. 12, Happ's OPS dipped below .600 on the season. In 27 games since that point, he has hit .366/.396/.782 with 11 homers, 19 extra-base hits and 25 RBIs. That includes his two-hit day on Sunday.

3) Heuer earning trust
After Steele's effort, relievers Codi Heuer and Rowan Wick each worked two sharp innings out of the bullpen. That had the Cubs in a position to attempt a late comeback.

"We came close today," Ross said, "strictly because of how the bullpen came in and shut things down. That's what great pitching does."

Heuer allowed one run on a wild pitch, but that represented only the third earned run yielded by the righty since joining the Cubs. After the White Sox sent Heuer to the North Siders in the Craig Kimbrel deal on July 30, Heuer has a 1.23 ERA with a .164 opponents' average in 22 innings. He has given up no earned runs in 16 of his 18 outings.

"Let's give credit to the player first, right?" Ross said. "He was pretty good. That's why we got him for a really good player. I think the front office identified his strengths, and he's fit in really well. He's got a little experience under his belt.

"He's a guy that seems to handle moments really well. He knows who he is. He continues to work to get better. There's a lot to like about him, and he's done a great job since coming over here for us and locking down a lot of the back-end innings for us."