Santana was scheduled to throw batting practice Tuesday, but pitching coach Dan Warthen said Saturday that the session had been canceled. Santana remains on a long-toss program and likely will throw from 150 feet Sunday.
Alderson said it will be 10 more days before Santana builds up enough arm strength to pitch in an exhibition game. He also said Santana has no structural issues in his shoulder and that an MRI hasn't taken place or been planned.
"We haven't ruled out opening day, although given when he might get on the mound, it becomes less and less likely," Alderson said. "But we haven't given up on that notion yet and we'll see where that takes us."
The two-time Cy Young Award winner didn't pitch in the major leagues in 2011 following shoulder surgery, then went 6-9 with a 4.85 ERA in 21 starts last year, when he pitched the first no-hitter in Mets history on June 1 against St. Louis. Santana didn't pitch after Aug. 17 because of lower back inflammation.
The 33-year-old left-hander did not throw much during the offseason, other than what Mets manager Terry Collins called "light tossing" in order to rest his arm and shoulder.
"I think there was an expectation when he came in that he would be ready to pitch, but I think that was his expectation, too," Alderson said. "Regardless of the winter that he had, I don't think there was disagreement, I don't think there was a disappointment on our part or an acceptance on his part that that's the way it would be. But it was clear over the first few days he wasn't ready. So we're going to get him ready."
Mets manager Terry Collins said he would rather have Santana miss the first few starts of the regular season than have his season cut short again.
"If he's not ready—if he's not where we think he should be, then there's going to be discussion about whether or not he's ready to start the season," Collins said. I know one thing, if he misses one or two starts at the beginning of the season, if he does, I know one thing, we'll have him throughout the summer because we'll have done this the right way and got him ready."
Santana gets $25.5 million this year in the final guaranteed season of his $137.5 million, six-year contract. The Mets hold a $25 million option for 2014 with a $5.5 million buyout.