Arsenal manager Arsene Wenger admits "surprise" at Alex Oxlade-Chamberlain's development as the 18-year-old forward claims his first two Premier League goals in a 7-1 win over Blackburn.

Robin van Persie's hat-trick, two goals from Oxlade-Chamberlain, Mikel Arteta's strike and Thierry Henry's late goal saw Arsenal move up to fifth in the Premier League.