Arsenal v Liverpool on Friday night had it all, didn’t it?

A six-goal thriller between two Premier League giants under lights just days before Christmas. Beautiful.

But even before the match caught fire, Liverpool had to change things around.

Captain Jordan Henderson appeared to pick up a hamstring injury after chasing Mesut Ozil and was replaced after just 13 minutes.

Many clubs would suffer after losing their skipper so early in a match but Liverpool looked better after James Milner replaced Henderson.

Within 13 minutes of the substitution, Liverpool were ahead and they dominated the rest of the first-half.

So, what changed?

Well, a tactical analysis video has emerged and it shows exactly what Jurgen Klopp did after Henderson came off.

The obvious change would have been Georginio Wijnaldum for Henderson but instead it was Milner - and there was a very good reason for this.

WATCH: TACTICAL ANALYSIS OF ARSENAL V LIVERPOOL

Check out the video which explains it perfectly:

So, to recap, Hector Bellerin’s forward runs were causing Liverpool a few problems early on so Milner came on to help out Andrew Robertson. This pushed the Arsenal right-back back and prevented him from getting forward.

Robertson himself likes to get forward so Milner, who played the entirety of last season at left-back, was deployed on the left-hand side of midfield to cover for him.

But that move meant Philippe Coutinho had to play on the right side of midfield as opposed to the left side, where he usually operates.

It was a great tactical decision from Klopp but he couldn’t do anything about the individual errors his players committed in the second-half.

Joe Gomez allowed Alexis Sanchez to nip in while Simon Mignolet somehow failed to save Granit Xhaka’s equaliser.