Chinese don't need to pressurize Russians in order to sabotage a s400 deal between Russia and India and that's not because of Chinese influence in Kremlin is limited but because Chinese know that the growing relationship of India and US will automatically halt this deal to ever happen in the future.
Let me explain you how;
First of all South China sea Islands are not only strategically important for China but for Russia too, because Russians for a long time have been thinking to somehow block this route that gives easy access to the US navy aircraft carrier's and because Russians consider their presence a threat to Russia's Sovereignty. And what India did recently is that they have joined forces with US to counter Beijing so called aggression in South China sea, rest if you are wise enough you will get the picture. Read this one out.
U.S., India join forces to counter Beijing aggression in South China Sea - Washington Times
Secondly, India is planing to buy defense equipment from US and from some of the European Countries. And if it does, Russia will most definitely cut its defense ties with India. (Russia has already threatened India about this one). And this is one of the 10 reasons that India has not been able to finalize the rafale deal with France.
And finally, things are getting worse for India, India wants to have a good defense related relationships with Russia and at the same time with US and Europe too. But things are not going according to what India has been planing for years as the world is changing so fast. Every single Country in the world is manifesting its own interests openly to the entire world. Things are different to what they were back in 70's and 80's.