Worst teammate ever? Club nemesis revels in Mat Ryan's World Cup howler

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Mat Ryan's FC Copenhagen teammate Kamil Grabara has added insult to injury following Australia's 2-1 defeat to Argentina in the round of 16 at the World Cup.

A touch too many following a backpass saw Ryan lose the ball and allow Albiceleste striker Julian Alvarez to score in the 57th minute.

While plenty were less than impressed by Ryan's decision-making in that moment, one person appeared more delighted than most in his misfortune.

"Must have been politics, for sure," Grabara tweeted with a smirking emoji. The tweet appears to reference not only the error in the Argentina game, but the pair's battle for the No. 1 spot in Copenhagen.

"I'm not surprised he did, to be honest," Ryan said after Australia's loss on Saturday. "It doesn't really concern me."

Grabara's tweet is just the latest chapter in this months-long, one-sided feud. The young Poland international has consistently disparaged Ryan publicly since his arrival in Copenhagen.

Australia captain Ryan joined the Danish Superliga side in August of this year in search of first-team minutes ahead of the World Cup. It was perfect timing for both parties with Grabara, the incumbent keeper who helped FCK to the league title last season, out due to a facial injury.

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Upon his return to full health, Grabara has consistently made claims that he should be the first-choice goalkeeper, often sneaking in jabs at Ryan in the process.

"I don't comment on my teammates' performances -- this applies especially when I haven't been in the games," Grabara told Danish outlet Tipsbladet in October.

"I can only repeat what I have already said -- I just have to state that there is a reason why we are in ninth place in the Superliga and that the goals have poured in. It speaks for itself.

"I don't see any competition for the goalkeeper position. I have every reason to believe that I am the first goalkeeper at FC Copenhagen."

Ryan, for his part, has vowed to come back stronger after his gaffe allowed Alvarez to steal in and secure a two-goal lead for Argentina.

"There were lots of positive moments we could take [from the campaign] and there were lots of tough moments and hardship," he said.

"That's exactly what I'm going to do with my error in the second half is try and learn what I can take from it and come back stronger for it.

"I haven't seen the replay, but I'll analyse it and I can only learn from it. We learn from our hardships in life and it's definitely one for me. It hurts a lot but I won't let it get the better of me or define me."

Ryan is said to be looking for a move away from Copenhagen in the January transfer window.