This number perfectly captures the Cubs' biggest weakness early in the season

Four eighth-inning walks from left-hander Luke Little cost the Chicago Cubs a chance at a fifth straight series win in San Diego on Wednesday, sending the club back to Wrigley Field for a five-game homestand against the Diamondbacks and Dodgers.

The bullpen has blown a handful of late leads in the early going, not to mention some bumpy early-season high-wire acts from closer Ryan Pressly, but the recurring theme has been the walks. Cubs relievers are tied for the MLB lead entering action Thursday with 41 free passes in just 71 1/3 innings of work.

Little's late-inning implosion is just the latest instance where control issues came back to bite the Cubs, who, despite the bullpen inconsistencies, sit in first place in the National League Central at 12-9. The bullpen ranks 27th in ERA (4.92) - and the hope has to be that things level off given the focus the front office put on this area last winter.

“We did make ourselves a hard [team to] beat,” Craig Counsell told MLB.com. “But you’re also kind of frustrated, because we probably feel like there was another game out there we could’ve won on this trip.”

Cubs hoping added bullpen depth will eventually translate to success

Jed Hoyer not only acquired Pressly but also veterans Ryan Brasier, Eli Morgan, swingman Colin Rea and veteran left-hander Caleb Thielbar. That doesn't take into account several non-roster invitees and minor-league additions such as Brad Keller, who has been an early bright spot on Counsell's pitching staff.

The Cubs had a lot of moving parts on the back end of the trip, placing Morgan on the IL and optioning Nate Pearson to Iowa - bringing in hard-throwing right-hander Daniel Palencia and Little, with Ethan Roberts also slotting back into the big-league mix this week. That's where the front office feels good: the sheer depth and number of options they've amassed here.

However, that depth hasn't translated to on-field results just yet - and the expectation is that, with more time, the cream will rise to the top. Keller has been a nice win for the front office and the man who finished last year as the team's closer, Porter Hodge, has been lights-out as the Cubs' setup man.

With the rotation tasked with going the distance without Justin Steele, the margin for error in the pen is already smaller than it was just weeks ago. The Cubs have to avoid digging an early-season hole for the third straight season if they want to be playing this fall - and getting the pen in order will go a long way toward helping them accomplish that goal.