#3 Ronald Koeman (Barcelona)
Ronald Koeman was handed over the reins of a club that has had their worst season in more than a decade.
After failing to defend their La Liga title, Barcelona were humiliated 1-7 by eventual champions Bayern Munich in the Champions League quarter-finals to end a season without a trophy for the first time since 2007-08. As if that was not enough, club captain Lionel Messi expressed his desire to leave the club before the start of the season before he changed his mind and decided to stay on for a season.
With the COVID-19 pandemic hitting the club's finances, Ronald Koeman had no big-name arrivals at the club and instead saw the prolific Luis Suarez leave Barcelona to join Atletico Madrid.
That coupled with the indifferent forms of Messi and Antoine Griezmann, Koeman's side has struggled in the Liga; they lost at home to arch-rivals Real Madrid and currently sit nine points off the league leaders after seven games. Even though Barcelona won 2-0 at Juventus in the Champions League, they are not tipped to go all the way in the competition this year.
If the former player is unable to arrest the club's indifferent form, and Barcelona endure another trophy-less season, Ronald Koeman's Camp Nou sojourn may end sooner than he may have hoped for.
#2 Ole Gunnar Solskjaer (Manchester United)
After overseeing one of the club's heaviest home defeats in history - Tottenham walloped ten-man United 6-1 at Old Trafford - Solskjaer's men lost to Arsenal at home in the Premier League for the first time in more than a decade.
In fact, Manchester United haven't managed to win any of their first four home games in the league for the first time since 1972-73, when they finished 18th. Considering the array of talent at his disposal, Solskjaer will hope that his team rediscover its form and turn around a rather dismal start to the season.
In Europe, Manchester United started brightly by winning their first two Champions League games of the season but fell to a disappointing defeat at competition debutants Istanbul Basaksehir.
It is not just the sequence of results but Solskjaer's questionable tactics and use of personnel in various games this season. A case in point is new signing Donny Van de Beek, who made a goal-scoring debut for the side but is not an automatic starter for Solskjaer.
If the Norwegian manager is unable to turn around his side's fortunes, he may not be around at the Old Trafford helm by the turn of the year.
#1 Zinedine Zidane (Real Madrid)
However, that is a very likely proposition, as Zidane's men have made an uninspiring start to their La Liga title defense this season and have also looked far from convincing in Europe.
Even though Real Madrid won at the home of their arch-rivals Barcelona, the Merengues were beaten at home by newly-promoted Cadiz. Madrid then lost 1-4 at the Mestalla to find themselves four points adrift of surprise league leaders Real Sociedad after eight games.
Real Madrid also made one of their worse starts to a Champions League campaign in recent memory. The record champions lost at home to a much-changed Shakhtar Donetsk before playing out an uninspiring 2-2 draw at Bayer Leverkusen. Rodrygo saved the blushes for Madrid in the next game after the side squadered a 2-0 lead at home to Inter Milan before managing to conjure a late winner.
Zidane is not in immediate danger of losing his job, but if Real Madrid fail to win the La Liga or go deep in the Champions League - they have lost in the Round of 16 in the last two years - this season, the French manager could be relieved of his duties at the end of the season.