The 22-year-old was called for the recent England squad after scoring nine goals across all competitions this season.
Azpilicueta said: "I had confidence in him because I have known him since he was quite young.
"Every time I saw him his work ethic was very good. Last season he had an amazing spell at Aston Villa, he was a key player for them, he scored a lot of goals.
"I knew he was ready for us and for the Premier League. As soon as he arrived he worked hard and wanted to help the team.
"Strikers live for goals so it's great for him. He's doing incredibly well and he scored an amazing goal. I'm very happy for him and I'm sure he can give us a lot more happiness in the future."