2003-04: Semyon Varlamov played for Yaroslavl's 1988-born team after playing his early hockey in the Samara hockey school in Russia.
2004-05: Varlamov made his men's league debut with Yaroslavl Lokomotiv’s second team in the Russian First League (3rd level) as well as playing for the U-18 team. In eight games in the First League, he recorded 1 shutout and had a 2.43 GAA. With the U-18 team, he was frequently a back-up to 1987-born Ivan Kasutin. Varlamov appeared in six playoff games for Lokomotiv U-18. Varlamov shared the goaltending duties for Team Russia with Ilva Proskuryakov at the WJC U-18 tournament. He was 2-1 with a 3.34 GAA and .904 save percentage in four games for fifth-place Russia.
2005-06: With Kasutin loaned to Penza, Varlamov assumed the starting job for Lokomotiv's second team. In 33 games, he had a 2.02 GAA and 8 shutouts. Internationally, Varlamov was a backup for Russia's U-20 squad and the starter for the U-18 team at the WJC tournaments. Varlamov stopped 19 of 20 shots in a 3-1 win over Latvia in his only game in Vancouver as Anton Khudobin handled the bulk of the goaltending for the silver medal-winning U-20 team. Varlamov started five games in Sweden for the fifth-place U-18 team and was 3-2 with a 2.82 GAA and .921 save percentage.
2006-07: Varlamov spent time in the Capitals' prospect and training camps before returning to Russia for his first season in the Russian Super League. The eighteen-year-old Varlamov and veteran Igor Podomatsky split the goaltending duties for Yaroslavl Lokomotiv, which had the seventh-best record in the 20-team RSL. Varlamov had a 15-7-6 record with 8 shutouts and a 2.12 GAA in 31 regular season games. In the playoffs, he played in 6 of 7 games as Lokomotiv swept Dynamo Moscow in the first round before falling to second-place Avangard Omsk three games to one in the quarterfinals. He finished with a 2.94 GAA in the playoffs. Varlamov represented Russia at the WJC U-20 tournament as was the second-best goalie at the tournament behind Canada's Carey Price. Varlamov allowed 9 goals on 136 shots (1.51 GAA) and was 5-1 with 2 shutouts as Russia reached the gold medal game before falling to Canada, 4-2. Varlamov was selected one of Russia's three best players for the tournament. Varlamov signed a three-year, entry-level contract with the Capitals in July.
2007-08: After attending Capitals camp, Varlamov was loaned to Yaroslavl in the RSL and took over the number one spot for Locomotiv. He was 27-15 with 3 shutouts playing in 44 games and had a 2.45 GAA and .909 save percentage for fifth-place Lokomotiv. Varlamov was even stronger in the playoffs as Yaroslavl made a surprising run to the championship round. In 16 playoff games, he posted 5 shutouts with a 1.62 GAA. Two of his five shutouts came in the best-of-five championship series with Salavat Yulayev. After stopping all 27 shots in a 3-0 win in the opener, Varlamov back-stopped Yaroslavl to a 1-0 win in Game 4 that temporary kept the club's championship hopes alive. Salavat clinched the title with a 4-1 win in Game 5. In international play, Varlamov was slated to play for Russia at the WJC U-20 tournament but could not play due to injury.
2008-09: Varlamov spent most of the season with Washington's AHL affiliate Hershey before taking over for the Capitals at the end of the season and in the playoffs. In a prelude of things to come, Varlamov made his first two NHL starts in December after being re-called due to an injury to starter Jose Theodore. He stopped 32 of 33 shots in a 2-1 win over the Canadians in his NHL debut on December 13 and then made 29 saves in Washington's 4-2 win over the Blues on December 18 before returning to Hershey. Varlamov appeared in two games for the Capitals in March and two more in April, and for the season won 4 of 5 starts with his only loss coming in overtime against Buffalo on April 3. Varlamov finished with a 2.37 GAA and .918 save percentage in six appearances for Washington. In the playoffs, Washington Capitals Coach Bruce Boudreau inserted Varlamov into the lineup as a surprise starter in Game 2 against the New York Rangers after an opening game loss. Despite out-shooting the Rangers (35-24) the Capitals lost, 1-0, to fall behind two games to none in the series. Boudreau stayed with Varlamov as the Capitals' starter. After coming back to defeat the Rangers in seven games, the Capitals lost a seven game series to the eventual Stanley Cup champion Pittsburgh Penguins. Varlamov played 13 games in the playoffs and was 7-6 with 2 shutouts and had a 2.53 GAA and .918 save percentage.
2009-10: Varlamov had the typical up-and-downs of an NHL rookie goaltender and also had to deal with a groin injury that kept him out of the lineup for almost two months. Playing in a tandem with Theodore, he had wins in 12 of his first 16 starts but had a habit of giving up goals in bunches. After suffering the injury in December, he played in just a handful of games prior to the Olympic break but seemed to get back into a groove at the end of March. In 26 games with the Caps, he was 15-4 with six overtime losses and had a 2.55 GAA and .909 save percentage. Following an overtime loss in Game 1 against Montreal in the first round of the playoffs, Boudreau once again turned to Varlamov and the Caps, who had the best record in the Eastern Conference during the season, appeared to get things straightened out – winning three straight games and taking what looked to be a commanding 3-1 lead against the eight-seeded Canadiens. In one of the classic NHL upsets, Montreal, despite being heavily out-shot, won the final three games of the series behind the outstanding goaltending of Jaroslav Halak to eliminate the Capitals. In six playoff games, Varlamov was 3-3 with a 2.41 GAA and .908 save percentage. Varlamov was selected for the Russian Olympic team in Vancouver but did not play as the third goalie behind veterans Evgeni Nabokov and Ilya Bryzgalov. He also appeared in three games for Hershey during his rehab, and was 3-0 with a 1.95 GAA and .933 save percentage.
Varlamov has a fairly unique, hybrid style and changes that style depending on the situation. Primarily a butterfly goalie, he will use his quick reflexes and fast reaction time to stop shots. He is quick to re-establish his stance after acrobatic saves and plays with a lot of composure. He has a quick glove hand but is not always active with his stick. Varlamov rarely leaves the net to play the puck, but is good at preventing one-timers by intercepting cross-crease passes with his stick. He plays a sound positional game and doesn’t lose the net. He maintains his poise and shows a lot of composure for such a young goalie. Conversely, he sometimes lets in bad goals due to a lack of focus, particularly when playing with a big lead. Varlamov has the size, raw skill and reflexes to make him into a strong NHL goalie. He continues to develop the maturity, mobility and stick handling capabilities that will allow him to become an elite goalie.