Gueye was sent off for beating a teammate! The last time the Premier League happened was the internal strife at Stoke City in December 2008.

In the 13th minute of Manchester United vs Everton, after Manchester United's attack ended, Gueye had a fierce argument with his teammate Keane and slapped each other, and was sent off by the referee Zhihong.
Statistics show that the last time a player in the Premier League was sent off for fighting with a teammate was back in December 2008 when Stoke City player Ricardo Fuller (conflicted with Andy Griffin).