Arsenal boss, Arsene Wenger said Olivier Giroud is a transformed player from the one he bought in 2012.
The striker's two goals against a down-beat Middlesbrough took Arsenal through to the FA Cup sixth round.
"Giroud is today a different player to the guy that arrived here," said the Arsenal manager. "He understands what top level football demands – he works with a great concentration in training and he has improved in his mobility tremendously and his technical quality. And of course his body is very strong and he uses it very well."
The Gunners manager also admitted he took a gamble starting Alexis Sanchez.
The Chilean international was a major doubt before the game after suffering a knee problem during the midweek win over Leicester City.
However, Wenger decided to use him and named him in the starting XI that eased to a 2-0 victory at the Emirates.
"He had a good performance. I think he became stronger as the game went on but because I took a gamble with him, I took him off with 20 minutes to go. He needed the game as well. He always wants to play. Everybody's like that but he's a bit more like that," Wenger told a post-match press conference.
Questioned whether the player is now more himself, he responded: "Yes.