Arsene Wenger says Aaron Ramsey's performance against Cardiff was "phenomenal", adding that the player's superb form continues to surprise him.
Ramsey scored twice as in the Welsh capital to go seven points clear at the top of the Premier League.
"He was phenomenal," said Arsenal boss Wenger. "He keeps surprising me. He has matured as a player and as a person.
"He can still develop. When you see the improvement in him in the last two years then why should he stop now?"
But this was the first time he had returned in a league game and the Wales international received a warm reception before kick-off.
After opening the scoring with a first-half header, Ramsey was applauded by sections of the home crowd - and some Cardiff fans sung his name following a second strike towards the end.
The 22-year-old did not celebrate but responded by tapping both hands against his head - a Cardiff celebration known by supporters as the Ayatollah.
"It's a special pressure when you come back to your home town," said Wenger. "He couldn't deal with that a few years ago.
"We came here in the FA Cup and he had a very difficult game, but now he shows how much he has developed as a person.
"The reaction of the fans was fantastic. We don't see that a lot and I would like to say to the crowd I really appreciate it."
Ramsey has scored 13 goals in all competitions this season and Wenger was asked if the Welshman could be prised from the club by an offer of £50m.
"No," the Frenchman replied. "We don't want to sell anybody, we want to keep the team together. I've suffered enough for years for having to sell the players. Now we are in a stronger position financially.
"I was a midfielder and would have loved to have what he has. He can defend, attack and score goals. What more do you want? He is also young - another quality that I have lost.
"There's more to come. If he continues to play like that then he will have a good future with Wales."