"It's not 100 percent. It would be, I would say, 95 percent," Rivera said. "By the time Spring Training starts, it'll feel 100 percent."
Rivera, 43, tore his right anterior cruciate ligament while chasing fly balls in batting practice in Kansas City last May, ending his season.
The all-time saves leader quickly put aside thoughts of retirement following the injury, vowing to go out on his own terms. He expects to resume throwing in about a week, which is earlier than he usually would be on a mound.
"It needs more strengthening. The five percent will come quick," he promised.
Rivera appeared in Connecticut on Saturday morning to conduct a pitching clinic with about 150 children at the Frozen Ropes baseball academy.
The three-hour event was attended by some students from Sandy Hook Elementary School in nearby Newtown, where a gunman killed 26 and wounded two on the morning of Dec. 14.
"We didn't try to get into it," he said. "We just tried to run it smooth and make sure they were comfortable. There were a few kids from there, and we want to make sure we made them feel comfortable and not try to treat them differently. I think that was for the best."
Rivera worked with the children on their leg lifts, arm slots and follow-throughs, nodding with approval when his instructions produced strikes, and patiently offering hints that might improve their performance in the upcoming Little League seasons.
Standing less than 15 miles from the site of the shootings, however, Rivera said it was difficult for him not to think about those events.
"When you have something like that and think about children, kids, I think the whole nation, the whole world, felt that," he said. "Not just the United States, but the whole world. It was a disaster, it definitely was, so all we have to do is pray."
The mood was considerably lighter with his laughing, chatty audience. Following the pitching clinic, Rivera fielded questions from the kids, saying in response to one query that he enjoys this side of the teaching process and that he hopes to continue instructing young players long after his retirement.
"I want to teach the little ones, because it's a long road from the Minor Leagues," he said. "That's where my passion is. I want to make sure those guys have enough guidance."
Rivera gleefully teased reporters with allusions to retirement last spring, but he doesn't seem prepared to drop any hints concerning when he might be taking his famed cutter home for good.
Asked by a youngster how much longer he intends to continue pitching, Rivera chuckled.
"There is media here," he said. "I don't know. I have another contract for this year. I don't know what is going to happen next year."
Rivera seemed much less concerned with the state of his knee than with making a good impression with his audience. Standing before the group of youthful faces, many clad in T-shirts bearing his No. 42, he hoped his message carried some weight.
"I feel good. That's what it is all about," he said. "We came here to take care and make sure that everything is done right. The most important thing is that they have fun, and that's what it is all about."
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.