Keegan tried to sign Peter Beardsley from Everton in 1993, but then-chairman Sir John Hall said the club would not pay £1m for a player who was at the twilight of his career.
KK told Hall Sunderland were going to sign him if Newcastle pulled out of the deal, and that was enough to get the transfer completed.
It's 15 years on, but the very thought of the Mackems getting the better of the Magpies is still too much to take.
Expect United to make an offer for the Spaniard within days.
Keegan has repeatedly been impressed by Cuellar and he could bid around £5m.