The England star says their victory at Liverpool is proof they're good enough to lift the Premiership title.
Walcott said: "We wanted to give something back to the fans because they were fantastic for us. We believe we can mount a challenge without Robin. He is such a big player for us - he has scored so many important goals for us and his stature up front scares defenders.
"He will be an unbelievable miss but we have got people like Andrey coming in to fill the gaps and he is fantastic as well. He will definitely clock up plenty of goals. It is fantastic to see but hopefully we can get our injured players back sooner rather than later.
"It is great to get these three points and gradually get closer to Chelsea and Manchester United. We have a game in hand coming up but we must look to Wednesday's game at Burnley now and aim to get the three points and we will be right there at the end of the season."