Euro 2016 is becoming the tournament of frustrated star strikers

Thomas Muller, remember him? The guy who scored 36 goals in 59 appearances in the Bundesliga last season.

What about Cristiano Ronaldo, he used to be impressive. 35 goals in 36 games in La Liga, wasn't it?

And Lewandowski, with all those records he broke last September. It can't have been five goals in nine minutes, can it?

That's without mentioning Harry Kane and Jamie Vardy, who battled it out for the Premier League's golden boot all last season.

These are all players who have been scoring for fun all season and yet not one of them has managed anything near his best during Euro 2016. What is it about the international stage that messes with their prolific strike records? Here are four reasons that could go some way to explaining this Euro 2016 mystery.