You can look it up. As of this very moment, with a record of 196-193, Don Mattingly's winning percentage of .503856 as manager ranks dead last in Los Angeles Dodgers history.
Call it unfair, call it a record that could stand for less than 24 hours -- call it ironic because it was Trey Hillman at the helm while Mattingly served a one-day suspension for his participation in Tuesday's brawl with Arizona that made the difference -- but the with the loss in Pittsburgh last night, the current skipper sank below Davey Johnson in winning percentage as Dodger manager, .503856 to .503864.
And it's worse than that. You have to go all the way back to Burleigh Grimes' .434 with the Brooklyn Dodgers to find a manager with a lesser mark. Circa 1938, which makes for a tidy round-number 75 years, if you're scoring. Don Mattingly, at least for today, has the distinction of being the worst Dodgers' manager in three quarters of a century.
Below is a screen shot from Baseball-Reference.com, the entire page of which shows where Dodger managers rank in various categories, going back to 1884 in New York. Note that Mattingly's record does include games played up until today, with the Hillman loss as part of it. If you click to Kirk Gibson's page, you'll see the same thing, even though Alan Trammell managed last night's game, while Gibby took his suspension for the fight. Ditto for Bruce Bochy, who also sat out a game after the Giants' Tuesday night fracas with the Bucs.
Please also note that while BR rounds down for Johnson, it rounds up for Mattingly, hence the discrepancy. Get out your calculator and figure it out for yourself. Wins divided by games managed. Or just wait for the Dodgers to win a couple of games, get on a little roll and play a better than .500 ball the rest of 2013.