Captain America can toss aside his shield and attempt to become Iron Man. David Wright is the latest Mets player questionable for Opening Day after tests in New York yesterday revealed the third baseman has a “moderate” left rib cage strain, an injury that surfaced while he was playing for Team USA in the World Baseball Classic. Wright, nicknamed “Captain America” for his heroics during the WBC, will rest for the next three-to-five days and then determine what activities he can resume. He officially withdrew from Team USA yesterday. Wright joins Johan Santana, who is building up strength in his shoulder and hasn’t yet made his Grapefruit League debut, among the Mets’ sidelined.