FAA goes long with the first point of his serve before edging ever closer to the net and producing arguably the fiercest smash of the championship so far to make it 15s each.

He follows that up with an ace.

No signs of weakness so far from the kid from Montreal.

Murray eventually holds with a 119mph ace. It's gutsy so far from the 33-year-old.

A good backhand from Murray and it's 30-0 but there follows a baseline rally which FAA stays on top of, forcing an error from the Scot.

30-15.

FAA is swinging Murray from one side of the court to the other like hardy people on a fairground pirate ship.

Unlike those people, this ride ain't stopping for Murray after just a few minutes.

Game to the young Canadian.

Saj Chowdhury here as JJ takes a breather.

How's our world number 115 doing?

Ahhh...

Leon Smith
GB Davis Cup captain on BBC Radio 5 Live

It would have taken a lot out of him that match against Yoshihito Nishioka. It will take him time to recover from that.

Andy will be looking to improve his first serve percentage (44%).

Auger-Aliassime is serving big and producing good forehand shots.

As good as that was from FAA, a word of caution... he's got to sustain that for another two sets.

That's also intended to provide hope for Murray fans...

Well. Incredible.

"Lights out tennis," is how Greg Rusedski describes FAA's performance.

Eighteen winners from the 20-year-old Canadian is why.

Murray survives the first set point but has to face another when FAA hits a carbon copy of that previous cross-court forehand winner.

Wow. The pair are scrapping at 30-30 before FAA pings off a truly wonderful cross-court winner off a body serve. Sensational.

Set point...

Leon Smith
GB Davis Cup captain on BBC Radio 5 Live

Andy hasn't managed a winner yet - he has not quite got the energy levels where he wants them to be, but there were signs in the last game.

Serving to stay in it, then.

Nope. That half chance is quickly snatched away from Murray. A wonderful cross-court winner, which kisses the apex, goes past Murray before even one of the great retrievers can see it.

That's FAA's 14th winner of the match - Murray still has none - and helps him hold.

"Let's go!"

The first trademark rally-cry from Murray comes when he punishes a FAA second serve for 30-30. Chance?

Who needs first serves when you've got touch like this. A deft drop-shot can't be caught by FAA, but Murray can't get over the line. Nor can he when he has advantage for a second time.

Third time lucky for the former world number one when a 113mph serve down the middle cannot be controlled by the young Canadian.

Nathan Smith: I hope this match lives up to expectation. Fighting sleep in the UK. Can't call it.

Murray looks a bit like I do the morning after I've been chasing people 15 years younger around a five-a-side pitch. A blank, slightly-weary expression, followed by the odd grimace if he moves too sharp.

The Brit starts finding his first serves, but that doesn't help him too much as FAA takes him to deuce.

Felix Auger-Aliassime is one of the youngsters who has been talked about for a loooong time.

Feel like he's not really broken through to a wider audience though due to not having a landmark win at a Slam.

Perhaps this would be it, even though it is not peak Murray.

Excellent quick hold. Three aces to finish. Good three-card brag hand that, not bad in a tennis game either.

Phew. Murray is on the board.

A wayward return from FAA puts the Scot within sight of the hold, Murray pounces forward and swatting away a winner to make sure.

One of Andy Murray's greatest strengths (and there are many) is his tennis brain: working out opponents quickly and adapting to what is front of him.

We see that in his first service point of the fourth game as he pins FAA back well behind the baseline and the Canadian is left scrambling. 15-0.

But Murray is struggling to land a first serve and that allows his young opponent to get into the game. 30-30...