Maguire's late drive handed Puel sweet revenge over his ex-employers as Leicester saw off 10-man Southampton 2-1 at St Mary's.
“It's a good reward for Harry and the team but I think we deserved this result," said Puel.
“Just before he shot I said 'give the ball, give the ball!'.
“He has a good shot. In training sessions, he works after. It was a good opportunity to shoot and in extra-time, the opponent cannot come back."