"We wanted to persuade him but it was in the Wigan game I saw his mind was elsewhere.
"Then it was a case of getting the best deal we could.
"It was disappointing but part of me understood as I spent a year on the transfer list myself."
Yakubu has yet to justify his £11.25million price tag and Southgate wants to show him what he left behind.
A Boro win would see them leapfrog Everton in the table.