Yes, the Cubs are for real. But how real?

Not everyone visits ESPN's baseball Relative Power Index (RPI) rankings to begin their mornings.

It's an obscure leaderboard, after all.

RPI is a measure most typically associated with college basketball tournament selections, as it combines the components of strength of schedule and team records to better evaluate the field.

But RPI is relevant to MLB nearly a third of the way through the season because a surprising team has resided atop the standings for much of the last month: the Chicago Cubs.

It's not only that the Cubs have exceeded expectations by scoring the most runs in the majors (10 more than the mighty Dodgers), or that they enjoy the NL's best run differential, or are tied for the second-most wins. It's that they've also done it while playing MLB's most difficult schedule to date.

The Cubs can make a case that they own MLB's top resume, fueled by the sport's best lineup, and with remaining upside: They've produced all these offensive fireworks with the wind blowing off Lake Michigan more often than not. Soon, it could be at their backs more frequently - a summertime tailwind.

It's an improved lineup that appears to have staying power, and that growth starts with Kyle Tucker.

Tucker's playing like the superstar he is. His addition not only strengthens the team based on his talent alone, but his left-handed bat lengthens a lineup and stresses opposing pitchers in ways that aren't quantifiable. And while adding a superstar is obviously a big deal, much of the Cubs' improvement is internal.

Shortstop Dansby Swanson's rebounded after a down 2024 season and owns a .262/.320/.471 slash line with 10 homers. He's one of the 50 most improved batters by wRC+ in MLB. While he started slowly, he's surged since late April, with a 1.133 OPS since April 27.

Of course, a veteran with a track record of improving off a down year isn't that surprising. Pete Crow-Armstrong, on the other hand, is arguably baseball's biggest surprise and perhaps the top breakout performer in the majors.

The center fielder is enjoying the fifth-greatest wRC+ improvement in the sport. He's already hit 12 home runs and stolen 14 bases. His elite defense was going to keep him in the lineup most days, but he's performing like a legit superstar now that his bat is playing at a different level. He trails only Aaron Judge in FanGraphs' WAR.

There are also team-wide improvements.

The Cubs feature the seventh-lowest strikeout rate (20.1%) after ranking 15th last season (22.3%).

They've improved while retaining key contributors like Seiya Suzuki (slugging .533 with 12 homers) and the steady Ian Happ. Happ and Suzuki have never been below-average hitters in 13 combined MLB seasons. They're strong supporting actors.

The Cubs don't have three Hall of Famers at the top of their lineup like the Dodgers, but they have eight batters with wRC+ numbers of 111 or better (minimum 94 plate appearances). That means even the bottom of their lineup is featuring above-average hitters - there are few easy outs.

And while Crow-Armstrong probably won't post a 40-40 season, and catcher Carson Kelly probably won't hit like peak Buster Posey all summer, the Cubs just recalled top prospect Matt Shaw, giving them upside at third base. Shaw appears to have found his timing during a Triple-A demotion after struggling early in the year. He could give the club a boost if it suffers regression elsewhere.

Add it all up and it's a deep lineup with staying power.

The real questions are on the pitching side.

The bullpen's littered with issues. The club acquired Ryan Pressly in the offseason, but the former Astros closer's stuff is in decline. He's been demoted from the ninth-inning role.

Porter Hodge was expected to be a high-leverage arm, and still may be, but he's struggling with command and is now on the IL. Their best reliever has been Drew Pomeranz, who's pitching at the big-league level for the first time since 2021. There's no sugarcoating it: The Cubs need relief help.

In the rotation, outside of Shota Imanaga (on the IL with a hamstring injury), the Cubs lack the type of impact arms to help propel a club through October. The rotation's 18th in fWAR, 19th in FIP, and 18th in Stuff+.

Matthew Boyd was their top offseason signing and is pitching well, but he hasn't reached 100 innings since 2019.

If we've learned anything from the Orioles over the last two years, it's this: A club enjoying an emerging lineup while dealing with pitching question marks should be aggressive in addressing those pitching issues. Tomorrow isn't promised.

In fact, another Cubs team with an elite cast of position players but pitching question marks added impact arms and broke a curse in 2016.

Tucker's a free agent at the end of the year. Crow-Armstrong may never have a season like this again. Happ and Suzuki won't always be above-average hitters. The time is now.

Travis Sawchik is theScore's senior baseball writer.