Santana threw three scoreless innings this past Thursday in his first rehab start since having shoulder surgery last September.
"He came back and didn't feel quite as strong as we would have liked," Alderson said. "Rather than force it, we're going to back it off a day and see how he feels tomorrow."
Alderson expressed confidence that the move was not as much a setback as it was a tweaking of Santana's schedule, adding that he would know Tuesday whether it was something more serious. Right now, Alderson said Santana is not feeling as strong as he'd like to feel, but he is not experiencing any pain.
"This is about not only being sensitive to what his body is telling him, but also, mentally, being confident to go out and throw," Alderson said. "That can have a lot to do with the mechanics and the outcome, as well."
In other injury news, Alderson said first baseman Ike Davis will continue running in Arizona for the remainder of the week before the Mets will evaluate him to see where they will go from there. The Mets have said in the past that if Davis isn't able to run without a setback in the near future, he will likely have surgery on his injured left ankle and miss the remainder of the season.
Additionally, Alderson said reliever Taylor Buchholz is unlikely to return to the team this season. Buchholz has not pitched since May 29 due to depression and anxiety issues.