Pienaar was one of the Toffees' players of the season and is currently preparing for this summer's World Cup finals in his homeland of South Africa.
The talented midfielder has just one year remaining on his Goodison Park contract and, while talks have been ongoing, it seems a deal is unlikely to be agreed during the finals.
Arsenal have been tipped to move for the South Africa international this summer and Wenger believes the former Ajax man has come on leaps and bounds recently.
Pienaar scored one of the goals in Everton's 2-2 draw at Emirates Stadium and Wenger has been impressed with how the ex-Borussia Dortmund man carried added responsibility during Mikel Arteta's absence.
"Pienaar has grown this year," explained Wenger. "He was usually a very busy player where the final ball was missing a little bit, but this year he has gained in personality and he has kept his work-rate, so he has been much more efficient.
"What also played a big role in his growth was that Mikel Arteta was not there for a while and that he had to take the responsibility of being the playmaker of the team.
"He was one of the best players in England this year. He would get into the Arsenal team. I always had an eye on him since he was at Ajax."