The former Sheffield United man produced a sublime display alongside John O'Shea to shut out City and pave the way for Ji Dong-won's last-gasp winner.
"I could see at about 10-15 minutes in Wes was struggling and before I knew it I was on," he told safc.com.
"To go on and play with such good players that we've got is a joy and we settled really well.
"It was a great result for the lads and we worked really hard to get it. It was hard to defend for so long.
"Everywhere you looked Man City's players seemed to find pockets and time seemed to fly by because we were concentrating so hard.
"I really enjoyed it; we played well as a team."