The 33-year-old left-hander was scheduled to throw on flat ground from 90 feet Saturday, up from 60 feet a week ago. He'll need to get up to about 180 feet before the Mets allow his first bullpen session since Feb. 6.
"I'm making progress; I just don't know when I'm going to be pitching again," Santana said Saturday. "That's the thing: We cannot think ahead. The way we're approaching everything is every day make sure we have a good today, so tomorrow we'll come back and we'll do it again until we feel we can do this without any problems."
The two-time Cy Young Award winner will miss the entire exhibition season because of a lack of arm strength and will start the season on the disabled list.
"It's a slow process," Santana said. "One day at a time, make sure that every day I feel better and make progress. That's what I'm doing right now."
Santana was examined by Dr. David Altchek earlier in spring training and was told his surgically repaired pitching shoulder is structurally sound.
Santana didn't pitch in the major leagues in 2011 following shoulder surgery. He went 6-9 with a 4.85 ERA in 21 starts last year and pitched the first no-hitter in Mets history June 1 against St. Louis.
His season ended in mid-August because of lower back inflammation, and he did only light tossing during the offseason, leaving him behind schedule when he reported to camp last month.
Santana acknowledged "not everything was there as far as my strength in my shoulder."
"Coming into this spring training I felt great. I was very excited and everything changed in a couple days," he said.
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.