Asked Wednesday if the cramping was related to having the coronavirus recently, Jackson said, "Probably. Probably because of the body heat and we're running in the cold. It was so cold out there. That probably had an effect on that as well. I can't call it."
Jackson tested positive for COVID-19 on Thanksgiving and acknowledged that he experienced flu-like symptoms. Team officials said Jackson was "hit pretty hard" by the coronavirus, and the quarterback said he spent most of his 10-day quarantine sleeping before returning to the team Dec. 6.
During Monday's dramatic 47-42 win in Cleveland, Jackson was in the locker room for the first 13 minutes of the fourth quarter because he had cramping in his throwing arm and both calves. He returned for the final two minutes to throw a 44-yard touchdown pass to Marquise "Hollywood" Brown and then put Baltimore in range for Justin Tucker's winning 55-yard field goal.
Jackson reiterated Wednesday that he was going through a lot of discomfort.
"I was real-life cramping, like my hand, my throwing arm cramping, forearm cramping, fingers getting stuck together," Jackson said. "I was going through it. I was ticked off."
Ravens coach John Harbaugh doesn't know if Jackson's cramping was related to the reigning NFL MVP recently having COVID-19.
"Who knows?" Harbaugh said. "Is it that? Is it the nutrition [and] the diet for two weeks? It's kind of a mystery. I think the doctors are trying to figure all that stuff out, too."
Jackson appeared on the sideline with two minutes remaining in the game, just when backup quarterback Trace McSorley hurt his knee on a third-down run.
Asked whether he would have returned if McSorley had not gotten injured, Jackson said, "I was actually getting stretched and I saw it was third down, I was getting up. I was already probably going out, if I'm not mistaken, I think I was probably already going out still. I don't even think it mattered. I was still going out regardless. I had to do it."
Jackson's target options also were reduced Wednesday, when Baltimore placed three wide receivers -- Brown, Miles Boykin and James Proche -- on the reserve/COVID-19 list. It is unknown whether they will miss Sunday's game against the Jacksonville Jaguars.
Harbaugh said all three wide receivers were identified as close contacts and didn't test positive. All won't practice this week but they will be eligible to be activated and play in Sunday's game if they continue to test negative.
"We're hoping and praying that they don't turn out to have it," Harbaugh said.