How long can Klopp's Liverpool keep playing with fire?

The hallmark of champions elect. That is the verdict on late Liverpool goal after late Liverpool goal.

In the past six Premier League matches, Leicester, Manchester United, Aston Villa and now Crystal Palace have been undone in the closing stages by Jurgen Klopp's side. Five goals, not one more than five minutes from time.

All five have changed the result, to the cumulative value of eight points. Liverpool's lead atop the Premier League? You guessed it.

They have won more points with goals in the final five minutes than any other team this season and at Selhurst Park it was Roberto Firmino who struck as the Reds extended their unbeaten run to 30 league matches.

This ability to dig deep at the death is testament to their fitness and fighting spirit. Not least given some of their squad were in the air as late as Thursday.

But among the superlatives and celebrations, is there cause for concern? Are late wins always evidence of a side's battling qualities, or rather a symptom of their fragility? After all, the 2-1 win at Palace was Liverpool's 10th straight match without a clean sheet. No one else in the division has been so charitable.

'Scoring late is good and enjoyable but we would much rather be 2-0 or 3-0 up and see out the game,' Andy Robertson admitted afterwards. 'We cannot keep relying on it but it is good we have that mentality and we did not panic, because we have been in this position so many times. That is why we took control of the game and scored the winner.'

He added: 'Maybe a couple of years ago, we would have had that setback and ended the game 1-1.'

The last time Liverpool failed to keep a clean sheet in 10 straight matches was more than 13 years ago.

True, only Leicester and Sheffield United have shipped fewer goals this campaign, but at this point last season Liverpool had let in just five and, though they are four points better off this time round, the signs aren't good.

Compared to last year, Liverpool are also conceding more shots and more shots on target per game. 'We have 37 points out of 39, so to say anything negative is harsh,' Robertson insisted.

'The defence and Ali (Alisson) and Adrian want to keep more clean sheets, of course we do, and today would have been a good one to get. Unfortunately it wasn't to be but if we don't keep clean sheets we need to be winning.

'Hopefully we can do that and still score goals. Last season we had a better defensive record, but did not have as many points, so we need to put it into perspective.'

Robertson is right, of course. But the bedrock of most Premier League champions has been a solid back four. At the moment they are being rescued by the forward line, but the issue will come if the goals dry up. Since the introduction of a 38-game season, the Premier League winners have kept an average of nearly 17 clean sheets. After more than a third of the season, Liverpool have just two.

So, rather than wondering how Liverpool keep finding late goals, should we be asking: how many times can one of the world's best teams expect to bail themselves out of trouble?

Liverpool's cause this season has not been helped by injuries to Joel Matip and Alisson. On Saturday they were hampered by an off-day from Trent Alexander-Arnold. Fortunately for them, for the second game running, VAR was on their side and even at 2-1 Wilfried Zaha missed a glorious opening.

It would be wrong to suggest Liverpool are riding high on good fortune alone. And though they have enjoyed the rub of the green, the scary thing is just how much better they can play. The question is whether their luck runs out before they rediscover those heights. Either way, something has to give.