Walcott: Arsenal improved thanks to Cesc, Nasri departures
Walcott says the departures led to the team adopting a new style.
The 22-year-old said: "Cesc and Samir were great team players but when you lose two top players everyone needs to come together.
"The manager has brought in some good additions and we are a bit more of a team, we work harder when we haven't got the ball.
"We have a lot more clean sheets as well, and having [Thomas] Vermaelen back is very important as he is a massive player for us."