The Premier League's biggest clubs collectively underperformed in 2o15-16. This summer, they have made certain 2016-17 will be much different.

The ongoing pre-season has been one of the most thrilling in the history of the league, accentuated by brilliant, marquee signings. Three Premier League giants— Manchester United, Manchester City and Chelsea— bagged themselves high-profile managers, too.

Now, arguably the top managers from the Bundesliga, Serie A and Premier League, will fight for the same trophy. Jose Mourinho, Antonio Conte, Jurgen Klopp and Pep Guardiola are all in the same division together for the first ever time and it promises to be an exciting season.

For the major clubs, expectations have never been higher. These are the finest managers in world football who know how to transform underperforming teams into champions.

Yet in today's Premier League, nothing is given to the top teams and parity has reached an all-time high. Leicester City's shocking triumph last season is proof. The four managers in their first full seasons will inevitably encounter hardships in such a competitive league from top to bottom.

But who will struggle the most?

Jose Mourinho

No league has proven too difficult for Mourinho to conquer.

He has won silverware at every stop of his illustrious career, including the Premier League, Serie A and La Liga. Add in Champions League and UEFA Cup victories, and the Portuguese manager has accomplished just about everything world football has to offer.

He remains in the Premier League after moving from one iconic club to the next. Last year, he was sacked at Chelsea after a horrid start to the season. Just months earlier, he led the Blues to a Premier League title in his second season.

Now he joins another club where winning is commonplace and losing is unacceptable. Despite the short turnover, Mourinho will thrive in his first full season.

He inherits a team that finished 5th in the standings last year. United's plodding style of play under Louis Van Gaal helped the club to a Premier League-best 36-goals conceded, but they struggled to score.

That won't be an issue next season. Mourinho attracted world-class attackers Zlatan Ibrahimovic and Henrik Mkhitaryan within a month's span. All signs point to Paul Pogba leaving Juventus for Old Trafford too, making United's new-look attack the most formidable in the Premier League.

United's super attack will lead United to a top three finish next year, at the very minimum. They will likely be the favourites to win the league, and understandably so.

Mourinho will prove again why he needs little time to form a winner.

Antonio Conte

Conte showed his managing prowess in the Euros, where he led a squad with minimal offensive talent to the final eight. Germany beat Italy on penalties, but their prior 2-0 triumph over Belgium, among other solid performances, are a testament to Conte's brilliance.

He inherits a Chelsea squad trying to salvage a horrendous 2015-16 season. One year after winning the Premier League, the Blues went on to finish 10th

The mediocrity from Eden Hazard, Cesc Fabregas and Nemanja Matic were the heart of the team's shortcomings. Conte will try to help the former standouts return to their dominant ways.

The Italian manager has already made a couple of marquee signings this summer, including striker Michy Batshuayi and N'Golo Kante. Former Leicester City star Kante was arguably the club's best player during their shocking Premier League title run. Batshauyi's goal-scoring will help Chelsea improve on their 59 goals scored last season.

Conte is also keen on finding a quality centre back. The Chelsea backline is ageing, with John Terry, Gary Cahill and Branislav Ivanovic all in their 30s. Regardless of personnel, Conte will maximise the potential out of the backline, just as he has shown during his days with Juventus and the Italian national team.

Overall, the Italian manager inherits a talent squad; it just needs some redirection. Conte, who led Juventus to three successive Serie A titles, is the man to guide Chelsea back to their usual winning ways.

Pep Guardiola

The mastermind behind Barcelona's possession-based, suffocating defence ployed squad, Guardiola is arguably the top manager in the world. Now he faces one of the biggest challenges of his career.

Pep inherits a Manchester City side that has finished in the top four in each of the past six seasons. The former Bayern boss will expect more success next season, but City have some wrinkles that need fixing.

Bolstering the centre back spot must be Pep's top priority, which he has clearly noted through his efforts to acquire Leonardo Bonucci.

Meanwhile, injuries have hindered Sergio Aguero and Wilfried Bony hasn't showed consistent form.

Needless to say, Pep has some work to do. He will need skilled tacticians across the field to employ his possession-based scheme. Finding players on the transfer who fit that mould is of paramount priority.

City will compete next year, but it will take Guardiola's brilliance, both on and off the pitch, for City to win the title.

Jurgen Klopp

The German has somewhat of an advantage over Guardiola and Conte because Klopp has already managed Liverpool for the majority of a season. But the talent on his side is inferior to other top clubs.

Needless to say, Klopp has some work to do this summer. Topping his priorities is finding a creative midfielder. Klopp is close to signing Georginio Wijnaldum, whose goal-creating ability will surely bolster the Liverpool attack.

Daniel Sturridge is surely Liverpool's top striker, although even his impact has has lessened in recent years due to injuries. Klopp must find a complementary striker that can find the net.

Meanwhile, the centre back and left back positions need reinforcing as Martin Skrtel departed Anfeld and Alberto Moreno struggled this season. Goalkeeper Simon Mignolet has struggled to justify his contract extension from January. Collectively, Liverpool let in 50 goals last season.

The Reds sat at 10th in the Premier League in October when Klopp took over as manager. The squad improved after his arrival, but their middling finish at 8th place indicates that changes must be made.

Of the four managers entering their first full season with their new squads, Klopp will struggle the most.

Between underperforming Liverpool players and the overall quality of the league from top to bottom, the 2015-16 season is one that will exclude Liverpool from a top five finish.