After the fourth GP, the 2001 Season witnesses changes involving three drivers:

 Though not entirely an ordinary occurrence, this sort of mid-Season driver replacement has had its precedents in F1.
 
 Current FIA Sporting Regulations allow every team one driver change for their first car and allows additionally three drivers for their second car.
   These drivers may be changed at any time, provided that the change be made in accordance with the FIA Code and before the start of qualifying practice.
   Independently of the number of racing events during which a driver works for a team, all drivers can challenge for points both individually and collectively (i.e., for the team).
   FIA Sporting Regulations require furthermore that the reason to consider the replacement of an assigned driver be a force majeure.
   As the examples below illustrate, however, the interpretation of force majeure appears to allow for a number of situations.
 
   Nowadays, most test drivers are capable of stepping in for either of the teams' official drivers.
   Last year (2000), Luciano Burti was rushed into Eddie Irvine's seat right before the Austrian qualifying session, when Jaguar's No.1 driver suddenly felt too ill to drive, and flew off to a clinic in London.
   Likewise, Pedro de la Rosa, who had so far had the role of test driver with Jaguar, was immediately promoted to Luciano Burti's vacant seat, as the Brazilian driver obtained from Jaguar a friendly termination of their contract, in order to drive for the Prost-Acer Team for the rest of the 2001 Season.
 
 The mid-Season change that is possibly remembered most clearly was Michael Schumacher's switch from Jordan to Benetton:
    M.Schumacher had proved his performance in one race with Jordan, who has traditionally provided the first seat to F1 talents, when the German rookie was snapped up by Benetton bosses, Tom Walkinshaw (now Arrows) and Flavio Briatore, in which team M.Schumacher went on to conquer his first title, two years later.
   This surprising move resulted in a wrangle between Schumacher's manager Willi Weber and Eddie Jordan, a dispute that was only placated with the interference of Bernie Ecclestone.   [ There is further reference to Eddie Jordan below ]   [ See also Eddie Jordan's reference to Jean Alesi, who was likewise a rookie at Jordan ]
 
 Jackie Stewart's replacement of Danish Jan Magnussen with Dutch Jos Verstappen halfway through the 1999 Season, at Stewart Grand Prix, had been the last time that a mid-Season change was effected for reasons other than injury.
   As in Mazzacane's case, and for basically the same reasons, there had been plenty of rumors prior to Magnussen's dismissal, even though the Danish driver did last longer than the Argentinean.
    Magnussen, who drove for Stewart Grand Prix for about half the 1999 Season, had arrived in F1 as a very promising talent and possible future champion.
 
 In the same Season (in 1999), Mika Salo's services were requested for Ricardo Zonta's seat at BAR for three races, while the young Brazilian recovered from injuries on his foot (Zonta's injuries were sustained during the practice sections for the Brazilian GP, which Zonta watched from a hospital bed). Zonta resumed his duties at BAR, after his recovery.
   Later on in the same year, Mika Salo (who, like Verstappen, had not managed to get a F1 seat at the start of that year), had his services requested once more, this time to replace no one other than M.Schumacher at Ferrari, while the German recovered from a fractured leg (during the Silverstone Grand Prix).
 
 Eddie Jordan seems to hold the record, as far as changing drivers mid-Season:
 
   In the 1991 Season, Italian Andrea de Cesaris and Frenchmen Bertrand Gachot were Eddie Jordan's official drivers.
   Toward the end of the year, however, five different drivers had taken his team to the starting grid: in addition to the drivers already named, Brazilian Roberto Moreno, German Michael Schumacher and Italian Alex Zanardi.
   Although de Cesaris remained as Eddie Jordan's steady driver, Gachot had to be replaced in order to serve a short sentence in jail.
 
   Alex Zanardi later moved on to the US CART Series, where he won the championship twice. He then made an unsuccessful return to F1, to partner Ralf Schumacher at Williams. Zanardi is currently back to the US CART Series, where he expects to regain his earlier form.
 
   Roberto Moreno also drove for Benetton in that same year (1991), subsequently moving on to the US CART Series, where he enjoys good prestige and races up to this date.
 
   Two years later, 1993, Eddie Jordan broke his previous record, with no less than six drivers defending his colors during that Season:
   Rubens Barrichello, who drove for the entire Season (and remains to date the driver who has worked the longest for Eddie Jordan), Ivan Capelli, Thierry Boutsen, M.Apicella (a former test driver at Jordan), E.Nespatti and Eddie Irvine.
   Brazilian Barrichello and Italian Capelli started the Season.
   As early as the third race of the Season, Boutsen replaced the Italian driver, for performance reasons (Capelli's two races had resulted in a crash out of one and a failure to qualify for the other).
   Boutsen's last race was in Hungary, after which Grand Prix he amicably retired from F1.
   For the following races, Eddie Jordan handed Boutsen's seat to Apicella (in Italy) and to Nespatti (in Portugal).
   The last driver to occupy Boutsen's seat along that Season was Eddie Irvine, whose explosive debut in Japan earned him a punch from a furious Ayrton Senna.   [ Check on Jaguar's driver replacements this Season (2001) ]
 
 In that same year, 1993, Michael Andretti (who, albeit more successful than Zanardi, never really managed to impress in F1, let alone repeat his father's feat) left the McLaren team after the Belgian GP, to be replaced by Mika Hakkinen from the Portuguese GP on. Hakkinen, as we all know, keeps his seat to this day.
   The Andretti's, it should be added, are a legend of their own in the US. Mario Andretti, who crossed the Atlantic to leave his mark also in F1, took the 1978 World Championship with the Lotus Team. His son Mario, whose achievements in the US have earned him great respect, came short of his father's reputation in the F1 scenario. Michael Andretti is still active, presently racing in the US CART Series.   [ Check on Mazzacane's replacement by Burti ]