Ronald Koeman believes the introduction of Romelu Lukaku as a first-half substitute provided Everton with the impetus they needed to help seal his first victory as manager in Saturday's 2-1 win over West Brom.
Gareth McAuley capitalised on slack defending to put West Brom into an early lead at The Hawthorns and Koeman made a bold move to bring on Lukaku in the 38th minute in place of James McCarthy.
It proved a shrewd move as Kevin Mirallas finished a free-flowing move on the stroke of half-time, before Gareth Barry converted from close range after the break to complete a hard-earned comeback in the Premier League encounter.
"It's a fantastic win because it is always difficult to come to this place, even more so when they go 1-0 up, but we played well," said Koeman.
"It's always hard to play against West Brom, the teams of Tony Pulis, because they have direct play and a lot of tall players and a lot of productivity from set-pieces and they scored from that.
"At 1-0 down we had to change the system. We needed a target man up front and to make the pitch a little bit wider and of course the 1-1 before half-time is vital.
"Lukaku and [debutant Yannick] Bolasie came on and both did well. We finished strong today. We can and must improve, but we are much better than one week ago."
As well as introducing Lukaku, Koeman switched systems and pushed youngster Mason Holgate - who was impressive throughout - to right back.
And Koeman singled out the former Barnsley defender for praise.
"I am very happy with his performance. He's doing well. Of course he makes some mistakes but that's part of football," the Dutchman said.
"He looks very comfortable in the centre-back position but also in the right-back position. He attacked well and he defended brilliantly, so it's good for the boy."
Koeman also confirmed that Lukaku - who looked set to leave the club in this transfer window - has now expressed his desire to remain at Everton for at least the coming season.