Why this week matters: Cubs face tough test, MLB's surprising slugger

Is it time to worry in Wrigleyville after the Cubs' tumble below .500? Scott Kane/USA Today Sports

What do you need to know heading into the new week? From struggling champs to healing aces, from a surprising new power source to some considerations about the trade priorities of one of baseball's best teams, here's what you should be checking out in a new week's worth of game days.

Will the Cubs start playing like the champs? This will be an interesting week at Wrigley Field, and I don't write that just because I have to be there. The Chicago Cubs host the Reds and Brewers in back-to-back series, two early surprise teams that currently are ahead of Chicago in the NL Central. The Cubs' run prevention problems are worse than they superficially appear since their solid team ERA doesn't account for their MLB-high total of unearned runs. Meanwhile, Milwaukee (second in runs) and Cincinnati (seventh) feature top-10 offenses. Can either or both of the upstarts hang with the Cubs and Cardinals for the near future? We may get a glimpse of an answer to that question this week. -- Bradford Doolittle