About the only certainty regarding the Mets’ leadoff spot is when Jordany Valdespin starts, he will bat first.

Otherwise, manager Terry Collins is still experimenting in search of stability atop the order. Last night, Valdespin made his second start this season as the leadoff hitter and went 3-for-5 in the Mets’ 7-3 loss to the Phillies. The three hits were a career high for Valdespin.

“When Jordany plays he’s going to lead off,” Collins said. “Because he is a different kind of player, maybe he really ignites you early by hitting a double or hitting one over the fence in the first inning.

“He’s got that capability, and he’s got capability if he gets on of stealing second and creating some runs. We discuss it every day and thought against [Kyle] Kendrick it would be a good guy to start.”

* Shaun Marcum threw a bullpen session yesterday in Port St. Lucie for his first mound activity in more than three weeks. Marcum is recovering from nerve inflammation in his neck.