We study the regularity of the Green current for semi-extremal endomorphisms of P 2 . Under suitable assumptions, we show that the pointwise lower Radon-Nikodym derivative of stable slices with respect to the one dimensional Lebesgue measure is bounded at almost every point for the equilibrium measure. This provides a weak amount of metric regularity for the Green current along holomorphic discs.2010 Mathematics Subject Classification. 37F10, 32U40, 28A15.