Johan Santana (shoulder) is scheduled to throw a light bullpen session Friday. Mets manager Terry Collins is encouraged by how Santana has looked thus far, noting that he isn't losing his arm slot and doesn't require lengthy intervals between throws. Still, it's hard to predict how his surgically-repaired shoulder will respond to the increased workload. The 32-year-old left-hander hasn't pitched in a major league game since September 2, 2010.