Mason, 25, suffered a fractured skull after colliding with the Chelsea defender 18 minutes into the Premier League game.
The midfielder was rushed to St Mary’s Hospital after receiving treatment on the pitch.
The former Spurs player is now in a stable condition after undergoing emergency surgery.
Hull City said he will remain in hospital for the next few days.
Many footie fans took to Twitter to post messages of support for both players.
But some ghoulish users attempted to spread false information, some in the moments after the brutal collision.
Many simply wrote “RIP Ryan Mason” as the player fought for his life.
Others peddled more blatant attempts to fuel speculation over Mason’s well-being.
One user named Ryan posted: “Ryan Mason has passed away. RIP you will live on forever. Can't believe this. I wanna run to you. Really can't believe this.”
A user named Awonke Bawuti wrote: “Sad day for football Ryan Mason is very bad he is expected to die in the next few days RIP.”
An account called the WeekDay wrote: “Rip Ryan Mason they told me Chelsea was going to be deadly this season and win the league but naw this is too much come on blues.”
Vic Breen blasted trolls peddling false information about the Hull ace.
He wrote: “Why are people tweeting rip Ryan Mason? He's in a stable condition. Let's all jump on the twitter bull shit. #RyanMason #GetWellSoonRyanMason.”
Other trolls targeted Gary Cahill for his part in the clash.
One fan, using the handle duckfarm97, described Cahill's challenge for the ball as a “dangerous, late head butt”.
Nick Tys wrote: “Whoever the f*** allowed Gary Cahill back on the pitch needs firing immediately.”
Not everyone was critical of Cahill over the collision as well-wishers shared messages of support for both players.
Matt Briggs wrote: “Both went for the ball, was a freak accident, clearly no intention to harm anyone.”
Tom wrote: “Thoughts are with @RyanMason and also @GaryJCahill as it probably isn't easy for him knowing what's happened today.”
Cahill, who continued playing, expressed his concern for the Hull star.
He said: “I tried to get on the end of the cross. We smashed heads. I wish him all the very best."
Sky Sports presenter Geoff Shreeves described it as a "horrific clash of heads" as the football world united to pray for his recovery.
