Barkley came off the bench at half-time to score the only goal against Leicester on Sunday.
And the Englishman says Chelsea's squad strength is keeping him on his toes.
"I'm focused, I'm feeling fit, I stayed on it when we were off, and I came back feeling good, training hard," Barkley told the club's website.
"Everyone is fit and on their toes, we have a lot of competition for places, and you have got to be ready when you get the chance.
On playing in empty stadiums, Barkley added: "I've adjusted to the empty stadiums.
"Seven years ago I was playing in reserve games with a similar empty stadium. It's just what we've got to do. We've adapted really well to it, with three wins out of three, but of course it would be much better with the fans in."