Southgate made the 27-year-old his first buy as a manager when he took full advantage of the Black Cats' relegation at the end of the 2005-06 season to snap him up for just £1.75million.

The Argentinian has since established himself as one of Boro's most consistent performers after being employed as a central midfielder, and will return to the Stadium of Light having gained a similar reputation with the fans on Teesside to the one he enjoyed at the Stadium of Light.

Southgate, who smashed his club's transfer record in January when he paid Heerenveen £12.7million for Brazilian striker Afonso Alves, is well aware of the value he has had from Arca and hopes there is still plenty more to come.

"Historically as a club when we have brought players in for lower fees, very often they have been the most successful signings we have made," Southgate said.

"If you look at the people we brought in this summer - Luke Young, Tuncay Sanli, Jeremie Aliadiere - none of them cost more than £2.5million, and they have all repaid that investment with their performances this year.

"Julio last year was the first player I signed and at the price we got him for, he has proved to be a bargain."

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