Willis, acquired in an off-season trade with the Florida Marlins, was on the disabled list since April 12 because of a hyper-extended right knee. He was 1-1 with a 4.41 earned-run average in three rehab starts at triple-A Toledo.
Right-hander Pedro Martinez of the New York Mets returned to the Dominican Republic to be with his sick father, delaying plans to test his ailing hamstring.
Martinez had planned to rejoin the club for a bullpen session Wednesday. But Martinez changed his plans after receiving an e-mail that said his 78-year-old cancer-stricken father, Pablo Jaime, had suffered a setback.
Mets Manager Willie Randolph issued an apology to team ownership, the club's TV network and the team's players "for the unnecessary distraction" he created by suggesting he was portrayed in a different manner than white managers.
Randolph, the Mets' first black manager, created a stir with comments he made that appeared Monday in the Record of Hackensack, N.J.
Randolph brought up race when he questioned the way he has been presented by SNY, the team's TV network.
Randolph said he wasn't asked by Mets management to issue the apology.