Rugby vs Football injury treatment rules

Greetings earthlings!

I wonder if any of you fine gents can help me out here!

I have been trying to educate one of my roundball following friends on the differences in rugby to football.  One of the things we are discussing is this strange rule in football where if you are injured you need to leave the pitch, even if it is just for a second.  You then need to walk over to the halfway line and get the ref's ok to rejoin the game!

This came about after the Scotland vs England roundball match where a Scottish Defender (think it was Hanley) went off and was walking up to the halfway line to come back on.  As he was doing this, england kicked a ball into the channel that the Scottish defender would have been covering and they scored a very important goal as a result.

I've been advocating that football follow rugby, if you are injured, the game continues! Get patched up and ready to go again as quick as you can!
My mind then went back to a game which I found hillariously funny.  I'm pretty sure it was Al Kellock in a Scotland international (6Ns or AIs maybe).  He went down injured and play move 20 metres up the park from where he was down.  The opposition then turned over the ball and either made a line break or kicked the ball back towards the Scottish line. 
If memory serves, Kellock saw play was coming back down towards him, shoved the physio out the road and either retuned the kicked ball or tackled the man who made the line break. 
 
Does anyone know what game this happened in? I'm trying to find a clip on youyube or that

Bit like Yarde on Saturday.Being treated for cramp, one of his team mates makes a break,he jumps to his feet, player runs past him,he receives pass & scores a try then continues to receive treatment.

One from Drico too. Around a minute or so in.

https://youtu.be/Ofho-CKSXX8

Because 99% of poofballers go down from the wind after free kick etc not many rugby players will take a dive if they go down its due to a genuine injury

broadlandboy wrote:Bit like Yarde on Saturday.Being treated for cramp, one of his team mates makes a break,he jumps to his feet, player runs past him,he receives pass & scores a try then continues to receive treatment.

surely he was in a form of offside for this one???