Riggs quit.
I'd say the day Davey took over (would have to look up the date...there was that couple of games with John McLaren as temporary manager.
The thing with Davey is that he uses so many players as almost-regulars. The late '80s Mets had several different lineups, just as the 2012 team does. Werth is out? So is Morse? Same with Ryan Zimmerman's shoulder? Harper takes over center...Moore plays some in left, Bernadina plays and shows he has improved, Lombo learns left field and third. The players just keep going.
Something Ron Darling said the other night: Davey never spots an expectation on a player. "He wouldn't say, 'If Hernandez hits .325"...he'd say, 'Well, Hernandez is going to get his 500 at bats, and Gooden and Darling are going to get their 30 starts, so we should do OK'. Davey puts the players in a position to do their best".