The former Leeds United midfielder is set to miss two to four weeks with a hamstring injury picked up against Preston North End on Wednesday.
The problem has been compounded by Nathan Wood being forced to isolate after his partner tested positive for Covid-19.
With four defeats in their last six games, Boro will be hoping Anfernee Dijksteel is fit to return from his own hamstring problem, and that Howson’s is not as bad as is feared.
“We’re not sure whether it will be a two-week or four-week job,” said Neil Warnock. “He’s had it for a few weeks. The doc doesn’t think it’s too serious.
“At Jonny’s age (32), there’s always going to be something shows up. It’s the wear and tear of little niggles over the years.
“We just think the radiologist has just gone a little too much in his estimations, so we’re sending it for a second opinion.“
Dijksteel has returned to training having missed the last couple of weeks through an injury picked up against Huddersfield but with Paddy McNair and Dael Fry the only other centre-backs available, Warnock has to be careful.
“We won’t get carried away just because we’re a bit short,” he said. “If we have to wait until Wednesday then we will do.”
Woods’s situation is a warning to a stretched squad.
“I’m stressing to the other lads, and not just them but their partners and their parents, we’ve got to be really careful now because it’s alright that they’re not in our bubble, but it still affects us.
“I got it (Coronavirus), so I can’t pick on anybody. You just can’t stress how vital it is that your bubbles away from here adhere to everything people are asking.”
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