Calgary Flames prospect Patrick Sieloff was not on the official roster USA Hockey submitted to the IIHF on Dec. 25 but the defenceman remains with the team in Ufa, Russia, practicing with the squad.
USA Hockey left a spot open on their roster, giving them flexibility to add another blueliner later on in the tournament.
"We are very close to finalizing our group of defencemen, pending the resolution of a medical situation," general manager of the 2012 US National Junior Team Jim Johannson said last week.
Matt Grzelcyk is also practicing with the team but not on the official roster.
Sieloff suited up for one of the Americans two exhibition games in Helsinki, Finland. He was paired up with Mike Reilly in the USA's 3-2 OT win over Sweden.
The Flames selected the rearguard in the second round (42nd overall) of the 2012 NHL Draft.