Boyle was the captain for the United States at the 2021 IIHF World Championship. He scored three points (two goals, one assist) in 10 games to help the United States finish third. He said during the Smashfest charity pingpong tournament in September that he was "trying to play" in the NHL this season.
"We really liked his game and we think he can help us in some of the areas where we're trying to improve and get better," Sullivan said. "Brian is a real good pro. He's really established himself as a real solid NHL player. He's had a great career to this point. We think he's a guy that is going to bring us leadership off the ice. We think he's a guy that's going to help us on the penalty kill and in the face-off circle on the ice. There are a number of areas where we think he can really help us. I thought he had a strong showing during the training camp so we're excited to have him and we think he's going to make us a better hockey team."
Boyle scored 15 points (six goals, nine assists) in 39 regular-season games in 2019-20 and one goal in four Stanley Cup Playoff games.
"Yeah, mentally being motivated to train was still there so I did it," he said. "Also, there wasn't much else going on. I still had a passion for it. I still wanted to get back in and play. It's obviously challenging but it's really a rewarding life to be able to play in this league so I'm excited to get back."
Selected by the Los Angeles Kings with the No. 26 pick in the 2003 NHL Draft, Boyle has scored 231 points (130 goals, 101 assists) in 805 regular-season games with the Kings, New York Rangers, Tampa Bay Lightning, Toronto Maple Leafs, New Jersey Devils, Nashville Predators and Panthers, and 31 points (16 goals, 15 assists) in 118 playoff games.
In 2018, Boyle won the Masterton Trophy, voted as the player who best exemplifies the qualities of perseverance, sportsmanship and dedication to hockey. He had been diagnosed with chronic myeloid leukemia, a type of bone marrow cancer, during training camp with the Devils in 2017 but returned to play Nov. 1 and scored 23 points (13 goals, 10 assists) in 69 games.
"A veteran presence," Penguins defenseman Kris Letang said. "He's been in the League for a long time. He's got a calm presence. Obviously what he brings on the ice, he's got a big size (6-foot-6, 245 pounds), big frame, he plays a physical game. Good two-way player. He's really effective.
"I've played a lot against him...just a hard-working guy. I've been on the wrong side of a couple of battles between me and him. It's fun to have a guy like that on your team now."
NHL.com senior writer Dan Rosen and independent correspondent Corey Long contributed to this report