The Cubs and the White Sox are both winning. Can they keep it up?

The big picture: The White Sox start the second half atop the AL Central, while the Cubs are firmly in the National League playoff race with a comfortable Wild Card lead.

The biggest surprise: The White Sox. After losing 100 games in three straight seasons, a young core has accelerated the rebuild behind strong starting pitching, timely hitting and late-inning heroics.

• Fans have responded by packing Rate Field, including sellouts against the Dodgers, Cubs and Guardians.

The biggest strength: Rookie Munetaka Murakami is back from a hamstring injury and the rotation remains intact.

The biggest concern: Key contributors like Murakami, Colson Montgomery and Noah Schulz have never endured a full major league season.

Reality check: The Sox have a lot of baseball to play inside their division, which includes the second-place Guardians and the streaking Twins and Tigers.

The other side (of town): The Cubs' first half was uneven, featuring two lengthy winning streaks and one prolonged skid. However, they're still well positioned for another postseason appearance.

• Injuries ravaged the starting rotation, with Cade Horton, Edward Cabrera, Matthew Boyd, Jameson Taillon and Justin Steele all spending time on the injured list. Closer Daniel Palencia also missed time.

• After a slow start following his offseason signing, Alex Bregman has begun heating up at the plate.

The biggest surprise: Young superstar Pete Crow-Armstrong has carried the offense. The Cubs' lone All-Star became the first player since Sammy Sosa to record 20 home runs and 20 stolen bases in consecutive seasons.

The biggest strength: This is a veteran team that should be getting some veteran pitching back.

The biggest concern: They're in a division with the Milwaukee Brewers, who are increasingly looking like a serious World Series contender.

The bottom line: Whether either club can finish the job remains to be seen, but Chicago fans have two playoff races worth watching.