By Bruce Levine–

CHICAGO (CBS) — Periods of success and failure have marked the rookie season for Cubs infielder/outfielder Ian Happ.

Arriving in the big leagues earlier than expected in mid-May, the 23-year-old Happ has displayed quality power. He hit his 18th homer of the season in a 4-3 win against the Blue Jays on Saturday afternoon. He’s also had growing pains at the plate, going through some slumps and striking out out a 29.9 percent rate.

“The games ebb and flow all the time,” Happ said. “That is why it’s a beautiful game and a terrible game at the same time. You will have your good days and bad days, good weeks and bad weeks. The thing is to just stay even and keep fighting through it is important.”

Along with teammate Kyle Schwarber, Happ is tied for the fastest to 18 homers in team history, accomplishing the feat in 80 games.

The strikeouts of something the Cubs can deal with when Happ is driving the ball, and he’s doing that with a .517 slugging percentage (tied for third on the team with Anthony Rizzo). The switching-hitting Happ has hit 15 of his 18 homers from the left side.

Happ has homered three times in the past three games he’s played. The Cubs enjoy seeing that, but they also remind him to stay consistent with his approach and be a hitter first. They want the power to come naturally and for him not to push for long ball fever.

“It is tough and a big adjustment,” Rizzo said of a young player’s progression. “It is a new everyday grind up here that is different from the minor leagues. He has hit his bumps along the way, but he keeps adjusting and keeps getting virtually better every day. It is fun to see his success eventually paying off.”

Along with Schwarber, Happ could be a poster child for the OPS era in baseball in which players are now valued highly for their ability to slug rather than hit for average. Happ is hitting .249 with an .838 OPS.

“The OPS has certainly become more prominent than batting average,” Cubs manager Joe Maddon said. “I think the strikeouts should be put into different buckets, depending on the situation. In order to get the product you are looking for, the process with young hitters must start in rookie ball. You raise them and then acquisitionally, you look for the same guy. I have always looked for the strikeouts and bases on balls being somewhat equal. The young guys who are expanders really only want to get hits. Everybody wants to get a hit, but the guys who are expanders want to get hits only. (leading to a low on-base percentage). Sometimes it’s about not making an out. That is what the young hitter doesn’t always understand. They must learn how offense plays (in team baseball) and not making outs.”

Happ has been used in all three outfield spots and second base as well, so he’s making an adjustments in many facets.

“I am comfortable here,” Happ said. “I have felt that way for a long time. I feel really great with this group of guys. Winning baseball games is a lot of fun.”

Bruce Levine covers the Cubs and White Sox for 670 The Score and CBSChicago.com. Follow him on Twitter @MLBBruceLevine.