The Panthers will pay half of Versteeg's remaining salary, according to Blackhawks general manager Stan Bowman. Versteeg is making $4.7 million per season and is signed through 2015-16, according to CapGeek.com. He had two goals and five assists and averaged 15:42 of ice time in 18 games for the Panthers this season.
Versteeg, 27, previously played for the Blackhawks from 2007 to 2010. He had 20 goals and 24 assists in 79 regular-season games, and had six goals and eight assists in 24 playoff games to help the Blackhawks win the Stanley Cup during the 2009-10 season.
"We're really excited," Bowman said after Chicago's 5-4 shootout win against the Phoenix Coyotes, which improved the Blackhawks to 12-2-4. "Looking at our team this year, we're off to a really good start. I think we've come out of the gates the way we wanted to, but we're always trying to improve. I think, looking at our team, we felt adding one more versatile forward to our group [would help us].
"I think just the experience and the versatility he brings to the table on top of the fact he's a player our coaches know well and players are familiar with. He brings a lot of energy, a lot of competitiveness, and he has a great skill level to complement our players, so we think it's a great fit and we're really excited."
Lefebvre will report directly to the Toledo Walleye of the ECHL.
Olsen, 22, was drafted by the Blackhawks in the first round in 2009. He played in 28 career games with the Blackhawks and 152 games with the Rockford IceHogs of the AHL.
Hayes, 23, was selected by the Toronto Maple Leafs in the second round of the 2010 draft and was later traded to the Blackhawks. He had six goals and seven assists in 43 career games for the Blackhawks, and has played in 120 career AHL games with the IceHogs.