The Football Association found the Chelsea captain guilty of racially abusing Queens Park Rangers defender Anton Ferdinand during a West London derby last October.
The length of the ban has prompted others to question the English governing body after they suspended Liverpool striker Luis Suarez for eight games, despite being charged with the same offence as the Chelsea centre-back.
"The fact he got a four-game ban, he may consider that is quite lenient considering Luis Suarez got eight," said Ferguson. "It is time to move on and so should the game."
Terry, who retired from international football last weekend, was also served a £220,000 fine.