Defenseman who was a first round pick of the Washington Capitals in the 2008 NHL Draft. He signed a six-year, $23.8 million contract extension with the team in 2012 and helped the team win a Stanley Cup title in 2018.
He played for the Indiana Ice of the USHL from 2006-2008 and the London Knights of the OHL during the 2008-2009 season. He made his NHL debut in 2009.
In 2010, he was voted to NHL.com's All-Time World Junior Championship Team. He co-captained the 2010 US junior team to a gold medal finish at the World Junior Championships.
He married his wife Gina Nucci in 2014. In 2015, his wife gave birth to their son Lucca.
He scored his first career goal against goalie Cam Ward in March 2010.