Johnson said: "I think at Man City once you start coming on as a sub, you do get classed as a bit of an impact player even when that's probably not even true. It is nice to be playing week in, week out.
"I think I've started more games for Sunderland probably than I did in the whole of last season. I think that tells you the story. My game is definitely benefiting from that. I feel much better physically.
"The team played higher up the pitch and it gave the attackers more chances. And then we didn't have as much space to cover getting back and forward.
"We're nearer the top half than the bottom three now and I think that shows the improvement in recent weeks. We beat City, we got a good win away at Southampton and I think things have picked up overall from earlier on in the season."