What’s up with the Dodgers’ Adrian Gonzalez struggling with LHP?

It is a riddle, wrapped in a mystery, inside an enigma. And I’m not talking about Russia or Justin Bieber.

The left-handed hitting Adrian Gonzalez has always taken great pride in his ability to defy baseball tradition and hit left-handers. And with good reason -- he’s a career .274 hitter against left-handers.

Only this season he’s batting .164 with a left-hander on the mound. This from a guy who’s batted over .300 against them in four different full seasons.

But right now, it’s a very real problem and has to be part of the reason Gonzalez, 32, is not in the lineup Monday against Reds left-hander Tony Cingrani.

In his last 11 games overall, the slumping Gonzalez is batting .108 (four for 37). Against left-handers he’s in an 0-for-20 skid.

Last season offered no indication that left-handers were suddenly becoming a problem. He hit pretty close to his career slash line of .273/.315/.432. This season, it’s been a completely different story. And so Monday it’s rookie Jamie Romak making his first career at first base.

Manager Don Mattingly hasn’t hesitated this season in starting all right-handed hitters against left-handers, save for Gonzalez. Now he’s out too, along with Andre Ethier, whose run as the everyday center fielder was oddly brief.

Ethier is sitting and Scott Van Slyke, who would normally spell Gonzalez at first, is in center. In essence, Mattingly is starting Romak -- who’s spent his last 12 seasons in the minors -- over Ethier and Gonzalez.

Ethier’s problem against left-handers is pretty long-term. He is hitting .179 this year and hasn’t hit over .222 against them the past four seasons.

For Gonzalez, though, this is new stuff and without easy explanation.