Their 1-0 defeat to Everton at the weekend was West Ham’s fifth league defeat in their opening seven league games of the season.
The Hammers are 18th in the league table and have been struggling to get their Premier League campaign going at the moment.
McCoist stressed that some of it is because West Ham do not have the squad depth to compete in Europe and England and keep their level of performance consistent.
However, he stressed that David Moyes is still entitled to feel disappointed about his team as, despite the Thursday-Sunday schedule and the travelling in Europe, West Ham should still be playing better.
McCoist said on talkSPORT: “I think there is an element of the Thursday-Sunday, I really do.
“You look at Manchester City, they effectively have two teams. They can change, they have got a strength in depth that probably no other team have.
“It’s tough for sides like West Ham to compete. The travelling can be tiring.
“However, I can understand David Moyes’ disappointment in the way they have performed.
“You can make, not excuses, but reasons with the travelling in Europe.
“At the same time, they should be putting in a better level of performance.”
West Ham will return to action after the international break with a home game at the London Stadium against Wolves on 1st October.
