Whether AJ (or SWP) play will be based on tactical decision - passing game or running game.
We now have verstatile players such as Milner who offer us tactical flexibility by changing their position / role mid game and other players who bring particular talents to the team - De Jong, AJ, SWP - who sometimes will play and other timesw not.
Johnson, and to a different degree SWP, represent something rare in British football - the ability to run past defenders - Johnson has a great trick where he knocks the ball off his standing leg to go between two defenders.
In the Liverpool game this ability was invaluable against Daniel Agger centre back playing out of position.
AJ's passing record, however, did not match the rest of the midfield:
AJ - 24 successful out of 33 passes made
Barry - 48 / 53
DeJong - 41 / 43
Milner - 29 / 36
Yaya Toure - 36 / 37
Tevez - 23 / 26
NB: Gerrard - 49 / 63 outpassed by Barry and DeJong
Benchmark: Scholes - 78 / 83 Fulham; 76 / 85 Newcastle