"Johan Santana's long-awaited clearance to begin a minor league rehab assignment came yesterday with the Mets' decision to allow him a 45-pitch debut.

That start will come tomorrow night for Single-A St. Lucie against visiting Daytona Beach. The Mets are hopeful it will lead to a return by their ace lefty at some point this season. Santana threw a bullpen session Sunday in Miami, convincing team brass he was ready for this next step.

Santana underwent surgery last Sept. 14 to repair a torn anterior capsule in his left shoulder. He told The Post last week that team medical director Dr. David Altchek indicated it would likely take a full year for Santana to pitch for the Mets -- though best-case scenarios pegged a return for late June or July.

Santana is hopeful for a return this season, but said his shoulder, not the calendar, will determine his pace."