||This article's lead section may not adequately summarize key points of its contents. (January 2013)|
|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)|
* Senior club appearances and goals counted for the domestic league only.
Castellazzi followed Brescia promoted to Serie A in summer 2000. He made his Serie A debut on 21 January 2001, against Vicenza Calcio. In 2001–02 season, he was the starting keeper for the Serie A team, but in next season lost his place to Matteo Sereni. After being loaned to Reggina and Catania in the 2002–03 season, he finally became regular starter again in the 2004–05 season, which he played all 38 Serie A games. Castellazzi initially the first choice of 2003–04 season, but lost his place to Federico Agliardi after round 4 and regained his place on round 23.
After Brescia were relegated to Serie B in summer 2005, he joined U.C. Sampdoria on a free transfer, signing a reported 2-year deal. He received the no.1 shirt from Luigi Turci. The first season he was the backup of Francesco Antonioli, and Castellazzi only played the 3 games that Antonioli missed.
In the second season, he finally earned a regular place, and in January 2008, he signed a contract extension again which would run until summer 2010.
In total, he played 101 league matches for the Genoese side, while his understudy 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 Inter Milan on a free transfer tying him to Inter until 2012. He became one of the understudies to Júlio César along with Paolo Orlandoni and replaced the retired Francesco Toldo. In 2010–11 Castellazzi played in all three major competitions, Serie A, Champions League and Coppa Italia, due to injuries afflicting César.
On 11 May 2012, Castellazzi signed a new contract with Inter, keeping him at the club until 2014.
- "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.
- "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.