Denisov spent most of his career from 2002 to 2013 at his hometown club Zenit Saint Petersburg, playing 354 games, scoring 29 goals and winning honours including three Russian Premier League titles and the UEFA Cup in 2008.

[3] Under Dutch manager Dick Advocaat, Denisov blossomed as a player, developing into an advanced midfield role behind Andrey Arshavin and Aleksandr Kerzhakov, becoming an influential member of the Zenit squad that won their first Russian Premier League title in 2007.

[3][5] On 3 April 2008, Denisov scored Zenit's fourth goal in their 4–1 first leg defeat of Bayer Leverkusen in the quarter-finals of the UEFA Cup match at the BayArena.

[6] Denisov's performances helped Zenit reach the final against Scottish side Rangers on 15 May, after defeating Bayern Munich 5–1 on aggregate in the semi-finals.

[8] In the resulting UEFA Super Cup, Denisov played the full ninety again, assisting Pavel Pogrebnyak's headed goal as Zenit upset English heavyweight Manchester United 2–1 on 29 August 2008.

[2] Six months later, on 22 December, Denisov was voted by the fans as the club's "Player of the Year", beating out the likes of playmaker Danny and goalkeeper Vyacheslav Malafeev.

[11] Denisov finished as runner up behind Malafeev as the club's MVP for the 2011–12 campaign, playing 57 games (starting all of them) whilst scoring one goal and providing eight assists.

[20] On 15 August 2013, Denisov moved along with fellow Anzhi players Yuriy Zhirkov and Aleksandr Kokorin to FC Dynamo for an undisclosed fee.

[28] Denisov made his debut for Russia on 11 October 2008 in a FIFA World Cup 2010 qualifier against Germany, a 2–1 loss at Signal Iduna Park in Dortmund.

[30] He featured in all three Group A matches,[citation needed] as Russia picked up four points but ultimately failed to qualify for the knockout stage due to their head-to-head record with Greece.

[31] On 7 September 2012, Denisov was appointed by new Russia manager Fabio Capello as the captain of the national team in the wake of Andrei Arshavin's absence.

[37] Media speculation reported that this pay strike was a result of Zenit's overhaul in the transfer market, bringing in Axel Witsel and Hulk on big contracts and in combined deals worth over $130 million.

[citation needed] On 7 April 2015, he was removed from training with the main Dynamo Moscow squad and transfer-listed by the team for "interfering with the work of the head coach" Stanislav Cherchesov.