Andre Onana gave away a costly goal against Groningen
The Eredivisie looks like a two-horse race between Feyenoord and Ajax this season.
Feyenoord went into Sunday's games with a five-point advantage over their rivals, but suffered a shock 1-0 defeat to Sparta in the Rotterdam derby.
In a league where the top-two rarely lose points, Ajax were given a chance to cut the gap to two points. Away to Groningen, the Amsterdam side looked likely to take the three points, despite being held scoreless at half-time.
Goalkeeper Andre Onana is a product of Barcelona's La Masia academy, and he has brought his ball-playing skills with him to The Netherlands. On Sunday, they let him down horribly.
With the ball at his feet outside the box, Onana easily evaded a tackle from Bryan Linssen, switching directions in the process. Getting ready to pass the ball to one of his defenders, Onana's right foot got caught in the ground, and saw him get intercepted at the second time of asking by Linssen.
The 26-year-old calmly rolled the ball into an empty net to give Groningen a surprise lead. Ajax would eventually equalise in the last ten minutes through defender Davy Klaasen.
Onana's mistake cost the team the shot at winning the game, and cutting the gap to two points at the top of the Eredivisie. He may not be so blase the next time he has the ball at his feet.