|Date of birth||19 July 1975|
|Place of birth||Gorgonzola, Milan, Italy|
|Height||1.92 m (6 ft 3 1⁄2 in)|
|1999||→ Pescara (loan)||3||(0)|
|2002–2003||→ Reggina (loan)||14||(0)|
|2003||→ Catania (loan)||18||(0)|
|2016–||Torino (Team manager)|
|* Senior club appearances and goals counted for the domestic league only and correct as of 16:57, 15 February 2016 (UTC)
Castellazzi followed Brescia promoted to Serie A in the summer of 2000. He made his Serie A debut on 21 January 2001, against Vicenza. In the 2001–02 season, he was first choice for the team but during the next season lost his place to Matteo Sereni. After being loaned to Reggina and Catania in the 2002–03 season, he finally became a regular starter again in the 2004–05 season, in which he played all 38 Serie A matches. Castellazzi initially the first choice of 2003–04 season, but lost his place to Federico Agliardi after matchday 4 and regained his place on matchday 23.
After Brescia were relegated to Serie B in the summer of 2005, Castellazzi joined Sampdoria on a free transfer, signing a reported two-year contract. He received the number 1 shirt from Luigi Turci. The first season he was the backup of Francesco Antonioli, and Castellazzi only played the three matches which Antonioli missed.
In his second season, Castellazzi finally earned a regular place, and in January 2008, he signed a contract extension again which would run until summer 2010.
In total, Castellazzi played 101 league matches for the Genoese side, while his understudies Antonio Mirante, Gianluca Berti and Carlo Zotti played 22 matches during 2007–08 to 2008–09 season, 11 matches and 1 match in 2006–07 respectively.
On 17 June 2010, Castellazzi joined UEFA Champions League and Serie A champions Internazionale on a free transfer, tying him to the club until 2012. He became one of the understudies to Júlio César along with Paolo Orlandoni and replaced the retired Francesco Toldo. During the 2010–11 season, Castellazzi played in all three major competitions – Serie A, Champions League and Coppa Italia – due to injuries afflicting the first-choice Júlio César.
On 11 May 2012, Castellazzi signed a new contract with Inter, keeping him at the club until 2014.
Castellazzi signed for Torino on a free transfer after completing his contract with Inter in 2014. He debuted for the Granata on 14 January 2015 in the Coppa Italia against Lazio, replacing Cristian Molinaro after the expulsion of Daniele Padelli.
- "Padova e Foggia, su la testa". La Gazzetta dello Sport (in Italian). 16 January 1999. Retrieved 18 June 2010.
- "Il Cosenza senza pace I tifosi contro Pagliuso". La Gazzetta dello Sport (in Italian). 17 July 1999. Retrieved 17 June 2010.
- "Bocciato Castellazzi De Biasi sceglie Saja". La Gazzetta dello Sport (in Italian). 5 October 2003. Retrieved 17 June 2010.
- "Castellazzi to give Sampdoria cover". UEFA.com. 25 July 2005. Retrieved 18 June 2010.[permanent dead link]
- "Castellazzi: "Vittoria e rinnovo del contratto, sono felice"". UC Sampdoria (in Italian). 26 January 2008. Retrieved 18 June 2010.
- "Inter Have Signed Luca Castellazzi From Sampdoria – Agent". Goal.com. 27 February 2010. Retrieved 17 June 2010.
- "Mercato: Castellazzi e l'Inter fino al 2012". FC Internazionale Milano official site (in Italian). 17 June 2010. Retrieved 17 June 2010.
- "Castellazzi signs two-year contract". F.C. Internazionale Milano Official Website. 11 May 2012. Retrieved 21 February 2013.
- "Castellazzi rinnova sino al 2016" (in Italian). Torino F.C. 4 July 2015. Retrieved 27 July 2015.