The left-back was withdrawn from the action at Portman Road on 59 minutes and replaced by on-loan Bristol City defender Cam Pring.
He was seen clutching the back of his thigh and shaking his head as he walked off the pitch.
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Now the manager has revealed it’s the same injury the 30-year-old picked up ahead of the Lincoln game at the start of November.
That setback saw the Blues vice-captain sit out five games over a three-week period.
Jackett doesn’t know the extent of the injury just yet.
But with important games against Fleetwood and Hull on the horizon, it’s feasible to assume Brown will not take part in either game.
Jackett told BBC Solent after today’s Portman Road game: ‘Lee Brown felt his hamstring, targeted it straight away, and has had to come off.
‘He had a similar injury at Lincoln, for which he recovered in a week or two.
‘I don’t know yet how long he will be out, but hopefully it’s not too long.
‘But, yes, a second hamstring injury of the season, which is a worry'.
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