races, he led Mansell to Ferrari 1–2 finishes. The championship once again came to the penultimate round of the season in Japan with Prost trailing his McLaren adversary, Ayrton Senna, by nine points. As in 1989, a controversial collision between the two settled the race. At the first corner Senna, as admitted a year later, intentionally drove his race car into Prost's, taking them both out of the race and sealing the title in his favour. "What he did was disgusting," Prost said. "He is a man without value." Prost finished the season seven points behind Senna, and his Ferrari team were runners-up to McLaren. Mansell left the Scuderia due to his unstable relationship with Prost, to rejoin Williams for the 1991 Formula One season. Mansell's replacement was Frenchman Jean Alesi, who had been impressive during the previous two years at Tyrrell. Ferrari had entered a downturn, partially as their famous V12 engine was no longer competitive against the smaller, lighter and more fuel efficient V10s of their competitors. The Ferrari chassis, despite a major revision by the French Grand Prix (F-643) was also not up to the level of the McLaren and the Williams models. Prost won no races, only getting onto the podium five times. He took this out on the team, publicly criticising the team and the Ferrari 643, and subsequently had his contract terminated before the end of the season, immediately prior to the . He was replaced by Italian driver Gianni Morbidelli for the final race of the 1991 season and by another Italian, Ivan Capelli, for the following season. Despite being sacked, Prost received a significant payment from Ferrari to not drive for any other team. 1993: Williams Prost went on a sabbatical year in , which was dominated by Nigel Mansell in a Williams-Renault. Prost performed pre-season testing for Ligier early in 1992 and later turned down an offer to drive for the team. After hearing that Prost would be his teammate again in 1993, Mansell left Williams to race in the CART series. Prost had a clause in his contract which prevented rival Ayrton Senna from joining the team that year. Prost was part of a new-look driver line-up at Williams, with test driver Damon Hill coming in to replace Riccardo Patrese, who had left to join Benetton. Prost won his fourth and final title in a year when he was regularly