Vardy has scored 21 Premier League goals this season to spearhead Leicester's phenomenal title charge and opened his England account by netting a wonderful backheel in the 3-2 win over Germany last month.
The striker was also on target in the subsequent friendly versus Netherlands at Wembley , where the 26-year-old Drinkwater impressed on his international debut in defensive midfield.
"If both are able to play like when they play for Leicester, definitely both could be contributing a lot for England, there is no doubt," Okazaki told Omnisport.
"I might not be the right person who can assess because they are big players [for Leicester] now.
"But I can say one thing, the key is whether they can do the same performance [for England] as in Leicester."
Drinkwater has forged a formidable midfield partnership with N'Golo Kante, who similarly broke into the France national squad in March.
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The 25-year-old scored on his first start – a 4-2 win over Russia in Paris – and Okazaki believes the call-up was a just reward for his exploits this season.
"He deserved to be called [because he is] the most important player for Leicester City," the former Stuttgart and Mainz forward said.
"He is a role model who shows his own character and strength fully every game and gets a good evaluation every time, as every player tries to do so.
"If Kante plays for France the same as for Leicester, I’m sure he can help France a lot. Kante is in the MVP-class of the Premier League this season.
"No doubt, if he continues to do so, he can succeed for France. It is without question."
On Wednesday, Vardy, Kante and Leicester winger Riyad Mahrez were all named on the six-man shortlist for the Professional Footballers' Association Player of the Year award alongside Arsenal's Mesut Ozil, West Ham's Dimitri Payet and Tottenham's Harry Kane.