Pritchard had told Sunderland he no longer wanted to be considered for selection and had subsequently been left out of the squad for their win over Stoke last weekend.
The 30-year-old is out of contract at the end of the season and told Michael Beale he is desperate to leave this month.
And talkSPORT understands that he is set to be granted his wish ahead of a prospective transfer to Birmingham.
It will see Pritchard reunite with Tony Mowbray, who he worked with at Sunderland before Beale's appointment earlier this season.
Mowbray took over from Wayne Rooney at Birmingham earlier this month with the club fighting relegation as they lie 20th in the Championship. Meanwhile, Sunderland seventh in the table as they chase a play-off spot.
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Pritchard's impending exit at the Stadium of Light will end close to three years at the club after joining in 2021.
The attacking midfielder has made 115 appearances for the Black Cats, scoring nine goals.
He joined when the club was in League One, helping them to promotion in 2022.
Sporting director Kristjaan Speakman confirmed last week that a contract extension had been offered.
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However, no agreement could be reached between all parties.
"Alex has been an absolutely integral part of how we've got sat around the Championship today in a really good position," Speakman said.
"He's a really important player for the group and I'm really pleased he'd got back in the team.
"His contract is up at the end of the season. From Alex's perspective we've offered him an extension to his contract.
"We felt, in conversations with him, that was something we needed to do, from where his head was at.
"He's in a really good position, I'm sure he's happy."