The Spaniard is believed to have confirmed that he will leave the successful club at the end of the season, with the 41-year-old expected to address the media this afternoon.
The news comes after the Spanish giants crashed out of the Champions League semi-final against Chelsea on Tuesday, just days after succumbing to Real Madrid in a 2-1 El Clasico defeat at the Nou Camp.
"It comes as a surprise to me, when you make a decision after a big disappointment like he had in the last week, it is not maybe the right moment to make that decision," said Wenger.
"I think as well that the philosophy of Barcelona has to be bigger than winning or losing the championship."
Wenger has been listed as one of the candidates to replace Guardiola at Barca in the summer.