When they needed it most, Argentina found their best performance of the World Cup so far as they defeated Poland 2-0 on Wednesday, a result that sealed them top spot in Group C and a last 16 meeting with Australia.

It has already been a roller-coaster ride in Qatar for the South Americans, who came into the tournament on the back of a 36-match unbeaten run under coach Lionel Scaloni, but looked rusty in their stunning opening 2-1 defeat to Saudi Arabia.

It immediately put them on the back foot in the pool, but they did enough to see off Mexico 2-0 in another unconvincing display in their second match, before a much improved showing against the Polish at Stadium 974, where they were roared on by the vast majority of the 44,089 crowd.

"We wanted to compensate for the defeat (against Saudi Arabia). Today it was a great game, we played very well collectively," Argentina goal-scorer Alexis Mac Allister said, adding the team did not let their heads drop after Lionel Messi missed a first-half penalty.

"We tried to stay positive, to stay calm. We did not feel down. We tried to be optimistic and go for the match. Fortunately we managed to win and go through."

There was more zip, better combination play and an altogether more polished Argentina on Wednesday, when they had 24 shots at goal, which suggests a theory put forward by Belgium coach Roberto Martinez last week may well be true.

Martinez said most teams will only be ready to compete in Qatar by their third pool game, given they had such little time to train ahead of the World Cup and some went into the finals without a friendly behind them.

"This tournament is going to make you develop and grow as it goes on. If you do that by winning games, it's an incredible advantage," he said.

Certainly the evidence when it comes to Argentina is compelling. They have got steadily better and saved their best performance for arguably their toughest pool opponent.

That should sound a warning to the other title hopefuls that Lionel Messi and co. are starting to click into gear. And they may have some more to go through yet.

Messi trundled around the pitch, only bursting into life when the ball was near him, showing again this is an Argentina side less reliant on him than those from the past, though that does not mean he is not an important player for them.

There are many other players in this side who are growing in stature and they too will be ready to face the Netherlands or the United States in the quarter-finals provided they can get past the Australians on Saturday. (Reporting by Nick Said, editing by Pritha Sarkar)