The Argentine forward is still an Atletico Madrid player but City are hopeful of concluding a deal for him over the next few days, and Johnson thinks that he would be a great addition to the squad.
The England international told Sky Sports News: “He’s Aguero a world class player. It would be great if he came and added to the squad that we have.
“I’ve watched him in La Liga over the last couple of seasons and he’s an outstanding player.”
Aguero scored 20 goals in 32 league games last season for Atletico and would clearly represent a like-for-like replacement for Carlos Tevez, a man Johnson still hopes will be at Eastlands next season despite heavy speculation about a move away, with Tevez having already seen a move to Brazilian side Corinthians collapse this summer.
Johnson said: “I don’t know whether he’ll be playing with us in the new season, that’s not for me to answer. I hope he is.
“Obviously he was our talisman last season, scored all of our goals and at times he’s carried us in certain games with his goals and his individual brilliance but he has his own reasons for what he’s doing at the minute.
“He’s a world class player and whatever he does I wish him all the best.”