Are you ready for a football marathon of unprecedented length and difficulty? The next year promises a run of fixtures and the longest period of competitive action that the game has ever seen after the Premier League returns from its coronavirus shutdown on Wednesday. It also promises to challenge elite players, both physically and mentally, like they've never been tested before.

There are 390 days between the Premier League restart and July 11, 2021, the proposed date for the final of the rearranged Euro 2020, and some players might only get a pair of two-week rest periods during that 13-month slog. Football has already returned in Germany, Spain and Italy, but while the top players in those countries also face tough months ahead, they can at least pace themselves through to the Euros. All three countries take a pronounced winter break and benefit from less congested fixture schedules, while the Premier League doesn't take a brief shutdown until February.

- Stream new episodes of ESPN FC seven days a week on ESPN+
- Insider Notebook: How much will Chelsea end up paying for Werner?
- Olley: Pulisic's place at Chelsea under threat?

In England, the leading players must prepare themselves for Premier League action, two domestic cup competitions (FA Cup, Carabao Cup), European involvement (Champions League, Europa League for the top clubs) and international fixtures. More so, some will compete in January's month-long Africa Cup of Nations, while others will play in the rearranged Euros and Copa America, all of which leaves little room for rest.

"It is going to be incredibly difficult for players," Dr. Tom Little, a sports scientist who has worked in the Premier League with Manchester City and Burnley, told ESPN. "I'm a big believer that athletes need some kind of break, both mentally and physically. But you also have to consider things such as the risk of injury and whether players are physically robust enough to rest up without exposing themselves to deconditioning.

"With what is going to be such a truncated preseason between the end of this season and the start of next, there are a lot of difficult decisions to be made."

For the top players, it promises to be a punishing schedule. For English clubs that reach the Champions League or Europa League quarterfinals -- both competitions are considering the idea of an eight-team mini-tournament in Lisbon and Frankfurt respectively -- they will have just two weeks to rest before the 2020-21 Premier League is scheduled to start on Sept. 12. So for the likes of Marcus Rashford, Raheem Sterling, Sergio Aguero and Paul Pogba, it could be a long time before they can achieve a few relaxing days on a beach.

"In most summers, the players will get at least three weeks to fully rest; they jet off to Los Angeles, Ibiza or Dubai. But they are unlikely to be able to do that this time," Little said. "Many will have had three months off during the lockdown, but without knowing when they would be back, it won't have been a proper rest period for any of them."

When it kicks off, the 2020-21 season will be relentless because the rescheduled Euros ensure that the end of domestic league seasons cannot extend into the summer. This despite, in many cases, leagues are expected to start a month later, in September, while the ongoing campaigns are wrapped up.

There's more, too. UEFA is still planning to stage the Nations League, with the prospect of two rounds of triple-headers before Christmas, while the European club competitions will run as usual, albeit with a later start date. Games will pile up, with the Carabao Cup and FA Cup expected to go ahead as usual, with only a 10-14 day winter break on the horizon in early February.

Kevin Kilbane, the former Everton and Sunderland midfielder, experienced the challenge of playing a full Premier League season and then a World Cup with the Republic of Ireland in 2002. He admits he had to programme his mindset before a ball was kicked in the summer of 2001 in order to be fit enough to perform in Japan and South Korea.

"I knew it was going to be a long slog," Kilbane told ESPN. "So I made sure from the outset that I had at least one day a week where I would put some miles into my legs."

"I played with Stefan Schwarz, the former Arsenal midfielder, at Sunderland, and he told me that he learned a big lesson from his experience of playing for Sweden at USA 94, where they reached the semifinals," Kilbane continued. "He said you had to make sure you arrived at the World Cup with the strength to cope with the demands after a long domestic season. So one day a week, I would get out the weights and hit the treadmill, doing 20-minute runs at high pace, then bursts at top speed or at the steepest incline.

"When it came to the World Cup, it stood me in good stead because I felt fit and ready for it. Nowadays, everything a player does is monitored by GPS, so there is no hiding place, but you do need to put the work in as well as get your rest."

Maintaining psychological fitness and freshness is another challenge the players will face.

"All I ever wanted to do was play at a major international tournament, so getting up for that wasn't a problem -- and it won't be for the majority of players," Kilbane said. "But nobody can escape the mental challenges of a long, hard season.

"Mental tiredness is a factor, which can be affected by everything from results and performances to what's happening [with friends, family] at home. Footballers aren't robots, and they need a break like everybody else. The pressure to perform consistently, for club or country, for 13 months cannot be overstated, so it will be a tough year or so for a lot of players."

Within the game, though, there is a belief that players simply want to play again after emerging from the longest period of inaction of their careers.

"The pandemic has affected everyday life on a global scale, and many things that wouldn't happen, or even be normal, prior to COVID-19 are now happening and are normal," Michael Dominguez, who works for Promoesport player agency, told ESPN. "So footballers are very excited to be playing again and looking forward to doing what they love -- being out on the pitch.

"All I hear is 'the more games the better,' because it will make up for the times they have been at home, wishing for football to return. Footballers just to want to play, and they are ready to adapt to the situation."

Adapting to the demands will be crucial. Without an understanding of what lies ahead, the longest stretch of competitive football ever known could feel like an endless battle of mental and physical endurance.