As the United Kingdom comes to terms with the death of its longest serving monarch, Queen Elizabeth II, several major sport events have been rescheduled or canceled.

The postponements and cancellations represent the latest disruption in a season which has already been dogged by congested calendar. It could place further strain on athletes, footballers in particular, who are facing a fixture pile-up.

Here's a look at the changes to the sports schedule:

Football

The English Premier League, Football League and the four football associations in Britain and Northern Ireland canceled all games this weekend. The decision came after an urgent meeting of the involved clubs even though sporting bodies were told by the British government that there was no obligation to postpone fixtures during the official mourning period.

Richard Masters, Premier League chief executive, said, "This is a tremendously sad time for not just the nation, but also for the millions of people around the world who admired her, and we join together with all those in mourning her passing.”

However, Masters' explanation has been quickly rebuked by the Football Supporters Association, which released a statement late on Friday saying that "most supporters would have liked to go to games and pay their respect to the Queen alongside their fellow fans."

It remains to be seen if next weekend's Premier League fixtures are postponed too as the funeral is expected to take place around that time. If that is the case, clubs will face a nightmarish fixture congestion later in the season. While the first-ever winter World Cup kicks off on November 20, there is almost no room in the schedule to squeeze more games in.

Boxing

All boxing has been canceled this weekend in the UK, including the much-anticipated world title fight between Claressa Shields and Savannah Marshall on Saturday. Shields is the holder of the unified WBA, WBC and IBF 160lb titles, while Marshall holds the WBO belt. Their blockbuster fight will settle which of them is the unquestionable champion of the division.

"This is an unprecedented moment in our history and our sincere thoughts are primarily with the Royal Family and the nation at this time. Out of respect, the British Boxing Board of Control has decided to postpone Saturday's show," read a statement.

"A provisional date for Saturday, 15th October at The O2 is being worked on by all parties to stage this unique and historical night of celebration for women's sport at a more appropriate time."

The organizers added that all tickets purchased for the event will remain valid for the rescheduled date. Existing ticket holders will be able to attend the newly-rescheduled event with their existing tickets.

Horse racing

The British Horseracing Authority has canceled all Saturday's fixtures, with the final day of the world's oldest Classic race "St Leger" being switched to Sunday. Musselburgh races on Sunday were called off due to the fact that Queen Elizabeth II's body will be moved from Balmoral Castle to Edinburgh.

Bill Farnsworth, general manager of Musselburgh Racecourse, said, "While protocols permit racing to resume on Sunday it would be inappropriate for us to stage our meeting as the Queen's body rests in nearby St Giles' Cathedral and as a mark of respect the decision was taken to abandon."

British Horseracing Authority chief executive Julie Harrington added Queen Elizabeth II had "an enduring and unique" relationship with the sport as an owner and breeder, and the return of some of the racings on Sunday will "provide an opportunity for the sport and its supporters to pay its respects to Her Majesty, for the contribution which she has made to the sport to be marked."

Meanwhile, golf's PGA Championship, Test cricket, rugby union and rugby league will return on Saturday following a day's pause.