The right-back, 22, had to be replaced in stoppage time of the heavy 6-0 loss at Stamford Bridge.

Patterson - who has regularly featured for Scotland under Steve Clarke - had come on as a substitute at half time but would need to be replaced before full time.

The defender pulled up after attempting to track back with Ben Chilwell with Sean Dyche warning of a "serious" hamstring problem.

The cruel injury blow is a serious worry for the player and the Scotland national team ahead of the Euros this summer.

No timeline for a diagnosis or rehab period was set in the aftermath of the match, with Dyche offering a "wait and see" verdict on the situation.

Patterson was just one of three injuries suffered by Everton in the nightmare loss with Jarrad Branthwaite and Seamus Coleman also forced off.

Dyche told club media after the match: “It was a perfect storm tonight. Every mistake seemed to get punished, every goal seemed to go in. I think they had 14 efforts on goal, we know how many we have had, they scored six - and we got three injuries.

“That isn’t a good mix, it happens now and again in your career and lifetime in football. But that is as bad as a mix I have experienced, with the injuries.

“Jarrad, we hope, is minor, but we have to wait and see. Shay (Coleman) has pulled his groin, we don't know yet and Patto’s looks a bit more serious. A hamstring injury, we are going to have to wait and see - let it settle tomorrow.”