Gibson wielded the axe just hours after the Teessiders had ended a run of three successive home defeats with a 2-0 victory over Derby ... but has he already got his man?
It's one thing throwing out the old ... but what do you replace it with?
He admitted the decision had been the toughest of his reign at the Riverside Stadium to date, but he could face an even TOUGHER decision finding a replacement.
Southgate did his post-match interview and it was obvious he didn't know the bombshell that was about to drop.
At around midnight, the club confirmed his departure in a brief statement.
Southgate was appointed by Gibson as Steve McClaren's successor during the summer of 2006.
It wasn't an easy post to fill either, because Gibson had to fight for special dispensation from the Barclays Premier League to give Southgate the job because he did not have the necessary UEFA Pro Licence.
He kept the club in the top flight with 12th- and 13th-place finishes but last season lost his way as Boro were relegated.