After playing four games in August with Monza, in the final days of the transfer market he accepted a move to Bari in Serie A, who paid 5 million lire.

After the match Bari-Reggina on 21 January, in fact, he became the first player in Italy to be indicted for testing positive for Nandrolone[1][2] and was forced by the sports court to serve a four-month disqualification.

Gillet remained a formidable goalkeeper: saving two penalties from Francesco Totti, during the two matches between Bari and Roma, and one from Robert Acquafresca of Cagliari.

[9] However, on 6 June 2013, in the aftermath of the Bari match-fixing scandal, he was indicted for sporting fraud and on 16 July was suspended for three years and seven months due to his role in the matches Bari-Treviso on 11 May 2008; and Salernitana-Bari on 23 May 2009.

[13] On 18 September Gillet played his first game as a starter for Torino since his suspension against the Belgian team Club Brugge, which ended 0–0 thanks to his heroic parries.

[16][17] On 17 March 2018, Gillet played as Standard Liège beat Genk 1–0 in extra time to win the 2018 Belgian Cup Final and qualify for the UEFA Europa League.

[18] Gillet became known worldwide for conceding 10 goals against Brazil at the 1997 FIFA World Youth Championship in Malaysia, in turn helping kick-start the career of Alex de Souza.

In August 2009, at the age of 30, after a strong performance against Inter Milan for Bari, Gillet was called up to the Belgian senior team in view of qualification for the 2010 FIFA World Cup against eventual champions Spain and Armenia.