Wigan, as revealed in Sportsmail, and Wolves lead the chase for the Argentine who is out of contract at the Riverside in June.
Mowbray said: 'There's not a lot we can do. He was signed when we were in the Premier League, on Premier League wages and his contract is expiring at a level that is unsustainable for us.'
With captain Matthew Bates ruled out for another six weeks at least, Mowbray is in discussions to take former Boro defender Andrew Davies on loan from Stoke City for the rest of the season.
Summer move: Arca will leave the Riverside when his contract runs out
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Source: Daily Mail
Source: Daily Mail