Alexei Semenov was born April 10, 1981 in Moscow, Russia. The 2nd choice, 36th overall selection of the Edmonton Oilers in the 1999 NHL Entry Draft, Semenov is a graduate of the OHL's Sudbury Wolves.
The hulking defenseman from Moscow, Russia spent three seasons with Sudbury where he was the recipient of the Max Kaminsky Trophy awarded to the Most Outstanding Defenseman in the OHL in 2001 after setting career highs in goals (21), assists (42) and points (63).
Semenov joined the Oilers AHL affiliate in Hamilton following Sudbury's 99-2000 playoff run and played three games with the team during the post season. Following a three game stint with Hamilton, Semenov returned to Sudbury for his final year in 2000-01 before becoming a permanent fixture on the Hamilton blue line in 2001-02.
After a strong season in 2001-02 with Hamilton, Semenov split the following season between the AHL and the Oilers before becoming a key component to the club's blue line in 2003-04. With the NHL players locked out in 2004-05, Semenov returned to his homeland and suited for SKA St. Petersburg before returning to the Oiler lineup in 2005-06. However, Semenov's stay with the Oilers was short lived as he was dealt to the Florida Panthers in the early stages of the season.
At the start of his 2006-07 season, Semenov was sent to the Panthers AHL affiliate in Rochester. He played four games with the Rochester Americans but was upset at his assignment to the club, and as a result opted to leave the team to play for Ufa Salavat Yulayev in Russia. Although Semenov did manage to compete in 23 games with the Panthers, he was signed in the off-season by the San Jose Sharks.