Shirokov first played in the Russian Hockey First League (RUS-3) with HC CSKA Moscow's second-tier team in 2001. He spent several seasons at that level and debuted with CSKA's senior team in the Russian Superleague in 2004–05, going pointless in eight games. The following season, he recorded 14 points playing 39 games in the Superleague. Shirokov was then selected 163rd overall in the sixth round of the 2006 NHL Entry Draft by the Vancouver Canucks. The sixth round draft pick was acquired by the Canucks in a trade with the Florida Panthers.
Though selected by an NHL team, Shirokov continued to play in Russia for HC CSKA Moscow and recorded a team-best and career-high 40 points in 56 games for CSKA, who competed in the newly formed Kontinental Hockey League (KHL) in 2008–09. He then turned down a tax-free $500,000 contract to stay in the KHL. Instead, Shirokov defected to North America and signed with the Canucks to a two-year, two-way US$1.75 million contract on 17 August 2009. The deal allowed him to make an annual US$875,000 at the NHL level or C$67,500 in the minor leagues.
Shirokov made an immediate impression in his first training camp with the Canucks, but suffered a minor setback during the pre-season, missing a week with an injured knee. He recovered in time for the end of the pre-season to lead the team in exhibition scoring with seven points in four games. As a result, Shirokov earned a roster spot for the start of the 2009–10 season, beating out fellow Canucks prospects Cody Hodgson and Michael Grabner.
Shirokov made his NHL debut on 1 October against the Calgary Flames, starting the season on the second line with Ryan Kesler and Mikael Samuelsson, as well as the first power-play unit. However, after going pointless in his first three games before becoming a healthy scratch, he was sent down to the Canucks' American Hockey League (AHL) affiliate, the Manitoba Moose on 8 October. Shirokov scored his first AHL goal in his Moose debut the next day against Drew MacIntyre of the Chicago Wolves, also adding an assist in a 4–1 win. After scoring 10 points in his first 10 games with the Moose, Shirokov was re-called by the Canucks on 25 October after an injury to forward Kyle Wellwood, but was returned to the AHL after three games on 30 October in favour of centre Mario Bliznak. On 30 December, Shirokov was chosen to Team PlanetUSA for the 2010 AHL All-Star Game. At the time of the selection, he was leading the Moose in scoring with 11 goals and 23 points through 33 games. He finished his first campaign in North America with 22 goals and 45 points over 76 games. Among AHL rookies, Shirokov was ninth in points and tied for third in goals. He added two assists in six playoff games as the Moose were eliminated by the Hamilton Bulldogs in the opening round.
Shirokov started the 2010–11 season with the Moose. After a slow start, he was leading the Moose in scoring with 33 points in 39 games, including a team record 12-game point streak, when he was recalled by the Canucks on 17 January 2011. In his first game back in the NHL the following day, Shirokov scored his first NHL goal against Craig Anderson in a 4–3 overtime loss to the Colorado Avalanche. After two games, he was sent back to the Moose on 23 January. Shirokov was selected as the Moose representative for the 2011 AHL All-Star Game, the second year in a row he would be at the game. He went on to complete the season with a team-leading 22 goals, 36 assists and 58 points in 76 games. As the Moose advanced to the second round of the 2011 playoffs, he led the team in scoring with 7 goals, while adding 3 assists for 10 points over 14 games.
In the off-season Shirokov signed a three-year deal with CSKA Moscow. Then on 9 July 2011, Vancouver traded his rights to the Florida Panthers for the rights to forward Mike Duco. In his first year upon returning to CSKA Moscow, he finished eighth in KHL point scoring and was named to the 2012 KHL All-Star Game. The following season, Shirokov participated in the 2013 KHL All-Star Game. On 5 November 2013, CSKA Moscow traded Shirokov to Avangard Omsk along with Maxim Goncharov in exchange for Alexander Frolov and Stanislav Egorsheva. On 19 December 2015 in exchange the Anton Burdasov and Peter Khokhryakov has joined SKA Saint Petersburg.
Shirokov made his international debut with Russia at the 2003 U-18 Junior World Cup, earning a silver medal while contributing four points in five games. He continued to play with the national under-18 team, helping Russia to the best records at the 2003 Four Nations and 2004 Five Nations Tournaments. At the 2004 IIHF World U18 Championships, he helped Russia to another gold medal in Minsk, Belarus, defeating the United States 3–2 in the final. Shirokov contributed two goals in six games.
Shirokov made the jump to the Russia's under-20 team in September 2004, posting the second-best record with Russia at the Four Nations Tournament. Several months later, he made his first of two appearance at the World Junior Championships. In 2005 he scored eight points in six games at the top under-20 tournament in Grand Forks, North Dakota, helping Russia to a silver medal finish, losing in the final to Canada. In April 2005, Russia hosted the Big Prize Tournament in St. Petersburg, where Shirokov recorded an assist in two games as Russia posted the best record.
The next hockey season, Shirokov competed in the under-20 Four Nations Tournament in September 2005, where Russia finished with the worst record of the tournament. A couple months later, he helped Russia to the best record at the Four Nations Tournament in November. At the 2006 World Junior Championships in British Columbia, Shirokov helped Russia to a second consecutive silver medal, losing once again to Canada in the final. He scored five points in six games.
Shirokov was a member of the gold medal-winning Russian teams at the 2012 IIHF World Championship and 2014 IIHF World Championship tournaments, scoring a combined five goals and seven assists between the two events. He scored a goal and an assist in the gold-medal match against Finland at the 2014 IIHF World Championship. He won a silver medal the following year at the 2015 IIHF World Championship in Czech Republic.All statistics taken from NHL.com
All statistics taken from Eliteprospects.com