he was in pain, his lighting showed to be 10x stronger than dooku's, and it shot back in his face, also he used alot of force, because the force shroud FELL, he couldnt maintain it ne more, because of the mass force he released on windu, BUT he dit OVERact about it, he wasnt in great pain, but he was hurting for sure, he was just pulling of an act so anakin would intervene ( spelling? ), mace WOULD eventually have won, he is more than experienced to fend of sids' force attacks, and his close combat is unmatched