The Cubs enter Friday at 70-50, a pace of 94 wins and good for the best record in the National League. And yet, they have had a gigantic flaw, at least to this point. The starting rotation has been pretty bad overall, pitching to a 4.17 ERA. That ranks them just 10th in the NL. 

There are problems when it comes to putting a competitive rotation out there day in and day out, and it looks like the only possible solutions must come from within the organization, given that there aren't really any good starting pitching names in the August rumor mill (like Justin Verlander last year, for example). 

The problems

Let's examine the opening day rotation. 

Jon Lester: In seven starts from July 8 through Aug. 11, Lester pitched to a 8.65 ERA, allowing an opposing batting line of .350/.420/.664. He gave up 11 home runs in 34 1/3 innings. Through his good first half run, there were reasons to believe he'd regress, and he certainly has in a big way. 

Yu Darvish: Of Darvish's eight outings, four times he allowed at least four earned runs while not completing five innings. He allowed exactly one run in each of his other four starts, but still, he's pitching to a 4.95 ERA and has only made eight starts. He's trying to work back from arm issues, but it's taking forever. He's on the 60-day disabled list now. 

Kyle Hendricks: His three-year ERA trend: 2.13, 3.03, 4.11. Uh oh.

Jose Quintana: The lefty has the worst ERA of his career by a decent margin. He's coughed up 20 home runs in 125 innings, and he's walking more hitters than ever (4.0 BB/9 compared to a career mark of 2.6). He's nibbling far too much, and that's an even bigger problem given that he has had terrible command for the most part. So he tries to nibble on the corners and either walks too many guys or misses with a middle-middle fastball that ends up in the bleachers. 

Tyler Chatwood: Ninety walks in 99 2/3 innings and a 5.06 ERA. Brutal. He can't take another start this season. [UPDATE: He's getting on Saturday, as the Cubs have had to place Montgomery on the disabled list]

The solutions?

Cole Hamels: He's pitching again Friday night, and he's been stellar so far (1.00 ERA, 0.83 WHIP, 20 K, 4 BB, 18 IP). If he keeps throwing well, replacing Chatwood with Hamels is a master stroke. 

Mike Montgomery: Montgomery has made 13 starts in Darvish's place, and he's 4-3 with a 3.08 ERA and 1.30 WHIP. Looking at the peripherals, Montgomery shouldn't be counted on as a frontline starter at all, but if he's your No. 5, you're in fine shape. That means the rest of the guys need to step up. As noted above, the Cubs just placed Montgomery on the disabled list, but there aren't indications it's a long-term concern. 

Lester: Very encouraging outing Thursday night in Pittsburgh. Lester was his old self: dotting the corners, staying down in the zone and mixing in his offspeed stuff effectively when needed. He only allowed five hits in six scoreless innings while striking out eight and not walking anyone. The command and stuff were as impressive as the line. Him staying in this mode the rest of the way would do wonders for the Cubs. Of course, it's always possible he goes in the other direction.

Darvish: It's been at least three weeks since the Cubs reported that Darvish has felt pain in his throwing program. He's progressed through throwing off flat ground and then bullpens to having thrown a few simulated games. He's now likely going on a minor-league rehab assignment this weekend, per the Chicago Tribune. It's possible he's back the first week of September. In Darvish's last three starts last regular season, he pitched to a 0.47 ERA with 21 strikeouts against one walk in 19 1/3 innings. He then allowed only two runs in 11 1/3 innings in the first two rounds of the playoffs before his high-profile, pitch-tipping meltdown in the World Series. He's capable of a strong run. It's also possible he won't be back at all. 

Hendricks: After giving up two runs in the first inning to the Cardinals on July 29, something seemed to click back in place for Hendricks with his stuff and command. He threw six more innings without giving up a run that game. Since then, he's been susceptible to one bad inning (and the bullpen gave up two of his runs on Wednesday, skewing his line), but overall has looked a lot more like the 2016 Hendricks than not. If he can get that one inning thing under control, the Cubs have something. Then again, he's been fickle, so he's a continued question mark. 

Quintana: I've got nothing here. There isn't much I've seen or in the profile that bodes well for the rest of this season. 

A playoff rotation of the good versions of Hamels-Lester-Darvish-Hendricks makes the Cubs the best team in the NL. A playoff rotation with Hamels, Montgomery and questionable versions of Lester and Hendricks is pretty shaky. 

The Cubs are good enough to win the World Series, but they need the rotation to come together, in addition to getting good/healthy versions of Kris Bryant and Brandon Morrow back. If these things don't come together, it's possible to see the Cubs bounced in the NLDS, lose the Wild Card Game or even miss the playoffs altogether. 

How this group comes together goes a long way in determining the path to and/or through the NL playoffs these last six weeks.