The past couple of months have been rough for Giants first baseman Brandon Belt.

With his availability for Opening Day already in question as he rehabbed from right heel surgery in October, Belt was forced to deal with another pair of setbacks at the outset of the year: a COVID-19 diagnosis in January and a more serious bout with mononucleosis in February.

Belt said he felt fatigued and lacked energy for about three to four weeks after contracting coronavirus, but he was hit harder by mono, which left him bedridden for about seven to eight days and forced him to miss over a week of full-squad workouts at Scottsdale Stadium.

“I couldn’t get out,” Belt said during a Zoom call with reporters on Saturday. “I’d get up to see my family and then I’d get right back in bed. I was probably in bed most of the day, a good majority of the day except for maybe an hour or two. Then once I got over the sickness part, it was pretty tough to get over the weakness that my body had and the lack of stamina, lack of energy, lack of strength.”

The good news is that Belt feels better now and is slowly easing back into baseball activities after overcoming his illnesses. He hit on the field for the first time on Friday and has also been throwing and running.

“Now I feel pretty dang good and every couple of days, I’m taking huge jumps forward,” Belt said. “I feel like I'm pretty close to getting back to normal. It was kind of a long ordeal. It obviously wasn't that fun, but right now, I feel like I'm getting back.”

Belt said his heel has been recovering nicely despite the interruptions to his rehab, though he acknowledged he’s unsure if he’ll have enough time to be ready for the Giants’ season opener in Seattle on April 1.

“Honestly, it's been going great,” Belt said. “I hadn't got to get out there and do a lot of things that I wanted to do over the last couple of weeks, but it's still been loosening up. It feels great. It feels so much better compared to last year, and now it's just a matter of getting the strength back in my foot and doing the day-to-day activities so that I can build the strength and the stamina up in my foot to be able to go a whole game. I don't think I'm too far away. I honestly feel really good and very optimistic about my foot.

“I don’t know if I’ll make it to Opening Day, but I’m going to try my hardest to get there. If I’m a couple weeks late, then that’s just what it has to be.”

Belt, 32, opened last season on the injured list due to the heel issue, but he returned after missing the requisite 10 days and went on to enjoy a stellar season. He hit a career-high .309 with a career-high 1.015 OPS and nine home runs over 51 games, drawing National League MVP votes for the first time in his 10-year career.

Belt’s future with the Giants is a bit murky, as he’s entering the final year of his contract with the club that drafted him out of the University of Texas in 2009, but he said his focus is on simply returning to full strength this spring and gearing up for another successful campaign in San Francisco.

“As big league ballplayers, we should treasure every season and every game because it could be our last at any time,” Belt said. “That’s not what I’m focused on right now, though. I’m focused on being productive.”

Belt thinks his “new heel” could help him take steps forward in other areas of his game, particularly his baserunning. Manager Gabe Kapler said Belt was up to 17 mph on the treadmill on Friday, leading Belt to joke that he expects to contend for the stolen base crown in 2021.

“My 50 percent is like everybody else’s 100 percent,” quipped Belt, who has 43 career steals in the Majors. “I think people are on alert.”