Monday night in Los Angeles, the Dodgers walked off with a win over the Giants (LA 2, SF 1) to stretch their NL West lead to six games with only 12 to play. It was a crushing loss for San Francisco, who is fighting to stay in wild card position.

The Dodgers won the game despite being shut down by Madison Bumgarner, who held Los Angeles to one hit and no walks in seven innings. He struck out ten and also got into a shouting match with Yasiel Puig. The Giants' bullpen melted down (again) and wasted their ace's gem.

Bumgarner is a great pitcher obviously, but getting dominated by a lefty is nothing new for the Dodgers. They are the worst hitting team against southpaws in baseball this season. Check out their platoon numbers (MLB rank in parenthesis):

vs. RHP vs. LHP
Batting Average .262 (6th) .211 (30th)
On-Base Percentage .329 (4th) .289 (30th)
Slugging Percentage
.439 (5th) .331 (30th)
OPS .767 (5th)
.620 (30th)

Geez, what a huge difference. The Dodgers are a top five offense against right-handed pitchers and the absolute worst against lefties this season. Their usual lineup is lefty heavy, but still, a team platoon split that large is stunning.

The Dodgers tried to address this weakness by adding Carlos Ruiz last month, but he's only one man. Puig and Enrique Hernandez have had disappointing seasons, and the Dodgers were counting on both to be big contributors against southpaws. Scott Van Slyke's season-ending wrist surgery hasn't helped either.

The Dodgers are hoping Yasiel Puig can help solve their issues with lefties. USATSI

Los Angeles has been able to open up a comfortable division lead despite that weakness against lefties for a few reasons. Monday night Clayton Kershaw and various relievers held the Giants down until Bumgarner was out of the game and the offense was able to go to work against the bullpen, for example.

Also, the Dodgers have only seen 40 lefty starters in their 150 games, so not even two a week. Roughly 28 percent of their total plate appearances have come against southpaws as well. There are way more right-handed pitchers than left-handed pitchers in baseball, remember.

This inability to hit lefties is an obvious weakness opponents will look to exploit against the Dodgers in the postseason, though it might not be that easy. Check out the pitching staffs Los Angeles could face come playoff time.

Chicago Cubs

Postseason Starters: Jake Arrieta, Kyle Hendricks, John Lackey, Jon Lester
Other Candidates: Jason Hammel, Mike Montgomery

Barring injury, the top four names represent Chicago's postseason rotation. They just have to figure out the order. Lester is the only southpaw among those four pitchers. Montgomery, another lefty, could be a factor out of the bullpen, especially since he's able to throw multiple innings. Travis Wood, Aroldis Chapman, and potentially Rob Zastryzny are the other lefties the Cubs will have in their relief crew.

New York Mets

Postseason Starters: Bartolo Colon, Robert Gsellman, Seth Lugo, Noah Syndergaard
Other Candidates: Gabriel Ynoa, Steven Matz, Rafael Montero

New York's rotation has been decimated by injuries this season. Matt Harvey and Jacob deGrom are done for the year, Zack Wheeler never made it back from Tommy John surgery, and Matz is out right now with a shoulder problem. He's scheduled to throw a bullpen session later this week and could rejoin the team after that.

As it stands the Mets have four righties in their postseason rotation. Unless they do something completely unexpected like start long man Sean Gilmartin in the playoffs, Matz is their only left-handed candidate for the postseason rotation, and the health of hishoulder will determine his availability. Jerry Blevins and Josh Smoker are New York's primary lefty bullpeners.

San Francisco Giants

Along with Matt Moore, Madison Bumgarner could create matchup headaches for the Dodgers. USATSI

Postseason Starters: Madison Bumgarner, Johnny Cueto, Matt Moore, Jeff Samardzija
Other Candidates: Matt Cain, Jake Peavy, Albert Suarez

With Bumgarner and Moore, the Giants have the best chance to derail the Dodgers with lefties among NL postseason hopefuls. Add in Cueto, an excellent right-hander, and a potential parade of lefty relievers (Will Smith, Javier Lopez, Josh Osich, Steven Okert) and the Dodgers probably don't want to face San Francisco in a short postseason series despite the Giants' second half fade. Their issues with lefties are real.

St. Louis Cardinals

Postseason Starters: Mike Leake, Carlos Martinez, Adam Wainwright
Other Candidates: Jaime Garcia, Alex Reyes, Luke Weaver

Garcia, the only lefty among those six pitchers, was recently demoted to the bullpen due to ineffectiveness. Would the Cardinals put him in their postseason rotation strictly to get a lefty matchup against the Dodgers? Maybe! I think you have to run your best starters out there in October regardless of handedness though, and at this point Garcia doesn't deserve a playoff start ahead of Reyes or Weaver. Kevin Siegrist and Zach Duke will present matchup problems for the Dodgers out of the bullpen.

Washington Nationals

Postseason Starters: Gio Gonzalez, Tanner Roark, Max Scherzer
Other Candidates: A.J. Cole, Joe Ross, Stephen Strasburg

If Strasburg gets healthy in time for the postseason, he'll be in Washington's playoff rotation, no questions asked. Either way, Gonzalez is the only southpaw starter the Nationals have available. Their lefty bullpen options (Oliver Perez, Marc Rzepczynski, Sean Burnett) aren't all that intimidating either.

Keep in mind that as it stands right now, the Dodgers and Nationals will meet in the NLDS. They both have big division leads and are unlikely to catch the Cubs for the top NL seed. Washington's lack of quality lefties could hurt against Los Angeles in the NLDS, regardless of whether Strasburg is healthy or not.

The Cubs and especially the Giants present the most matchup difficulties for the Dodgers, though Chicago's lefty depth is mostly in the bullpen. There are some potential matchup headaches in the AL -- both the Red Sox (David Price, Drew Pomeranz, Eduardo Rodriguez) and Rangers (Cole Hamels, Derek Holland, Martin Perez) could have three lefties in the postseason rotation -- but we're getting ahead of ourselves. The Dodgers have a long way to go before worrying about World Series matchups.

For now, the Dodgers have a very real and potentially fatal flaw in their utter inability to hit left-handed pitching. They're not just below average against southpaws. They're literally the worst hitting team in baseball against lefties. That's an exploitable weakness, however based on the potential postseason matchups, the Dodgers might not have to worry about it at all. It's possible they won't even face the Cubs or Giants. The best way to beat Los Angeles is with lefties, and few teams have the rosters to do it.