Ronald Koeman cannot wait to see his defence up against Sergio Aguero on Sunday, a player he has compared with former Barcelona teammate Romario.

The Saints boss likened Manchester City front man Aguero, who comes into Sunday’s game at St Mary’s on the back of a midweek Champions League hat-trick against Bayern Munich, to his one time Brazilian colleague.

Romario is widely considered one of the greatest strikers of all time and scored 34 goals in just 46 games for Barcelona when Koeman was part of the side at the Nou Camp.

“I think that the best player to compare to Aguero is Romario,” said Koeman.

“I played with him but sometimes you think he is sleeping and in one split second he is scoring and that’s a big quality because that means a lot of concentration for the defender.

“He’s always fast, he’s always on the edge of offside and that’s his best quality.”

Aguero has 17 goals to his name already this season but is coming up against English football’s meanest defence with Saints having conceded only six times all season.

It is a mouth watering prospect.

“That’s the nicest part of football sometimes that you can’t do everything to stop a player because he’s one of the best players, in my opinion, who makes in the last few weeks the difference between winning and not winning for City,” reckoned Koeman.

“Of course they have a strong squad and strong team but the last few games Aguero has been scoring and creating, and creating opportunities by himself.

“We have a strong defence and it’s a nice challenge for our defenders to keep the zero behind this Sunday.

“You can’t give them one second no attention, you need that attention during 90-95 minutes and that’s a great challenge to our defenders.”