Chelsea manager Mauricio Pochettino fumed his Chelsea side were not 'mature enough' after seeing his side twice surrender the lead to draw 2-2 against bottom side Sheffield United.
Thiago Silva and Noni Madueke scored either side of the break to put Chelsea 2-1 up, with Jayden Bogle scoring for the Blades just after the half-hour mark.
Just when it looked as though Chelsea were on course to claim all three points, McBurnie struck in the third minute of stoppage time.
'At 52, you identify really quickly whether the team is ready to compete or not.