Chelsea boss Thomas Tuchel took off Billy Gilmour at half-time with Callum Hudson-Odoi replacing the midfielder.
Tuchel revealed after the game that the substitution wasn’t because Gilmour performed badly but it was only tactical.
Tuchel said: “We put Mason there because we saw they defended so deep and we wanted Mason, who has a better shot from 20 metres, to maybe be more dangerous from distance and have an offensive player like Mason there.
“So it was not because Billy was bad, it was a tactical change to try to put more offensive power there.
“We lacked N’Golo [Kante] and Kova [Kovacic] in midfield today and this is huge for us.
“It’s not fair to put it all on Billy’s shoulders but he did okay, after a fantastic match against City. He was by far not the problem.”