The Northern Ireland international has made 215 appearances for the club since arriving from Sheffield Wednesday in 2007, but he has struggled to break into Steve Clarke's side this season.
He has only started two matches in the Premier League and has been singled out as the subject of some negative reactions from the stands.
However, Downing believes that Brunt is an asset to the team and has backed him to show his true value again.
"He's got pass rates, he's got assists, he's a consummate pro," Downing told the club's official website. "He leads the group and has a high regard within the group and he is experienced in terms of the position he plays.
"I suppose the formation, with the two holding midfielders, and us being more attack-minded in the wide areas, may have affected people's perception.
"He's an influence in the middle of the park who keeps things moving, we know what value he brings."
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