If we assume that Tokugawa can more or less solo Ohmagari and Inui, I don't see why it'd be impossible for him to do the same against Tanegashima/Sanada. Like previously discussed, Mu shouldn't be useable the same way it is in tennis and if we're talking about physical stats, Ohmagari is actually the same as or better than Tanegashima everywhere. And while Sanada > Inui, I still don't see Tanegashima/Sanada being coordinated in any way really which should be factored in.
If Sanada only serves at Kadowaki, even assuming Kadowaki is so terrible that he can't do anything about the serve, it's also super predictable, so Tokugawa should still be able to step in.