Fiorentina purchased Baggio in 1985 for £1.5 million. During his time at the club, despite initial injuries, he became extremely popular, and is regarded as one of the clubs best ever players. In his 1985–86 Serie A with the club, Fiorentina finished in fifth place in Serie A and reached the semi-finals of the 1985–86 Coppa Italia, with Baggio making his club debut in the competition. He made his Serie A debut on 21 September 1986 against U.C. Sampdoria, and he also made his European debut that season on 17 September 1986, in an 1986–87 UEFA Cup match against Boavista F.C.. Baggio suffered another knee injury on 28 September, and he was operated again, requiring 220 stitches to have it rebuilt, losing 12 kg as a result and missing most of the 1986–87 Serie A. Baggio returned, and scored his first league goal from a free-kick on 10 May 1987 in a 1–1 draw against Diego Maradonas S.S.C. Napoli, the eventual Serie A champions; Baggios equaliser saved Fiorentina from relegation.
Question: How many days before Baggio made his Serie A debut did he make his European debut?
Answer: 4