Son has been a key man for Spurs this season, scoring 18 goals in all competitions and starring in a central position when Harry Kane was out with injury earlier in the campaign.
"[Tottenham's] recent form has shown what a good side they are and what a good manager they have," Walker told City's official website.
"Son has been on fire and he deserves everything he gets. He is a very close friend of mine and the boy is so nice.
"He wouldn't say boo to a goose, he is that nice. He deserves everything he gets. His hard work is paying off for him."
Son found the net 21 times last term, having only hit the target on eight occasions in his first season in England in 2015-16.