The native of Gothenburg, Sweden, was the centerpiece of a package for Tyler Seguin, Rich Peverley and Ryan Button. He was shipped to Boston on July 4 along with Joe Morrow, Reilly Smith and Matt Fraser.
"It went by pretty quickly once it happened," Eriksson told Swedish newspaper Expressen. "I had no idea."
Eriksson, who had a limited no-trade clause as part of his contract, agreed to accept the move to Boston.
"The decision was obvious," he said. "It's hard to say no to Boston."
Drafted by the Stars in the second-round (33rd overall) of the 2003 NHL Entry Draft, Eriksson has played in 501 career NHL regular-season games, and has accumulated 150 goals and 207 assists for 357 points.
He's cracked the 70-point mark three straight times prior to this past season, with his most productive offensive season coming in 2010-11 when he picked up 27 goals and a career-high 46 assists for a career-high 73 points.