By 90min Staff Cristiano Ronaldo is set to be the subject of an investigation after appearing to make an obscene gesture in response to Lionel Messi chants at a Saudi Pro League game. The Portugal international opened the scoring for Al Nassr in Sunday’s 3-2 victory over Al Shadab, with a second-half brace from Anderson Talisca securing all three points. At full-time, fans could be heard shouting ‘Messi’ – a long-time Ballon d’Or rival for Ronaldo during his time in European football – and videos on social media captured the former Real Madrid, Manchester United and Juventus forward’s reaction…