Chelsea are hosting Arsenal at Stamford Bridge in today's early kick-off in the Premier League.
The Blues, who lost to Arsenal 3-0 in the reverse fixture earlier this season, took the lead thanks to Marcos Alonso after 13 minutes.
Alonso sprung up to beat Hector Bellerin to the ball in the Gunners' penalty area and head the ball past Petr Cech.
However, some fans on Twitter took issue with the use of his elbow which seemed to hit Bellerin in the face as the pair jumped for the ball.
Anywhere else on the pitch that's a foul...leading with the forearm #CHEvsARS— Always a red #mufc (@stavros_k9) February 4, 2017
That should not stand. Forearm smash by Alonso #CHEvsARS— CO-47 (@SadFactory) February 4, 2017
Part of me is thinking great goal, other saying it's a foul...#CHEvsARS— P A T E R S O N (@Patersonnn) February 4, 2017
However, others just thought Alonso was stronger than Bellerin.
Bigger. Stronger. Better #CHEvsARS— Jason Hathaway (@JasonMGO) February 4, 2017
How easy is that. 2 v 2 in the box #CHEvsARS— Danny Laino (@Dannylaino18) February 4, 2017