Jaromir Jagr, Thomas Vanek and Andrei Markov are among the unrestricted free agents still on the market.
What can an NHL team expect from these players this season? Here's a look at underlying numbers that provide some insight:
Jaromir Jagr, RW
Jagr, 45, can be described as a free agent with a high upside and a significant downside risk.
At his best, Jagr could lead the NHL in even-strength scoring rate, as he did with the Florida Panthers in 2015-16, with 2.70 points per 60 minutes, according to Hockey Analysis. That season, he set the record as the oldest player to lead an NHL team in scoring, with 66 points (27 goals, 39 assists) in 79 games.
Last season with Florida, Jagr's scoring rate was 1.75 points per 60 minutes, and he had 46 points (16 goals, 30 assists) in 82 games, a drop of 21 points. It is impossible to predict if this trend will continue, because two players have competed in the NHL past age 44 (Gordie Howe and Chris Chelios).
Though Jagr may be able to play at a top-six level, it is safer to expect him to reach 40 points on a secondary scoring line. Anything above that would be another age-defying bonus.
Video: FLA@TOR: Jagr pushes in a rebound for late PPG
Thomas Vanek, LW
With 48 points (17 goals, 31 assists) in 68 games for the Detroit Red Wings and Panthers last season, Vanek is the highest-scoring remaining unrestricted free agent. His even-strength scoring rate of 2.61 points per 60 minutes ranked sixth in the NHL among those who played at least 20 games.
Can Vanek score 48 points again? The chances are greatest if he is deployed in a similar fashion, which is on a secondary line and primarily in the offensive zone. His average of 11:45 minutes per game at even strength ranked 10th among Detroit forwards, and his average of 11:36 ranked 11th among Florida forwards. Vanek led each team's forwards with zone-start percents of 72.68 and 63.51.
Vanek also can be of value in the shootout, where he was 5-for-5 last season, bringing his NHL total to 28 goals in 67 attempts (41.3 percent).
Andrei Markov, D
The highest-scoring remaining defenseman is 38-year-old Markov, who had 36 points (six goals, 30 assists) in 62 games for the Montreal Canadiens last season. His 0.58 points per game ranked 16th among NHL defensemen.
Most statistically comparable defensemen experienced a drop going into his age-39 season. Larry Murphy, Larry Robinson, Kimmo Timonen, Sergei Gonchar, Mark Howe and Chris Chelios fell from an average of 0.52 points per game at age 38 to 0.25 at age 39. That works out to 22 points in an 82-game season.
To use a more recent example, Mark Streit's scoring fell from 52 points in 81 games for the Philadelphia Flyers in 2014-15 (when he turned 37) to 23 points in 62 games in 2015-16, and 27 points in 68 games in 2016-17.
Even if Markov's points drop, his value goes beyond scoring. He is a two-way defenseman who kills penalties, takes on top opponents in both zones, and drives possession. He can be used in the shootout, where he has five goals in 14 attempts (35.7 percent).
Video: OTT@MTL: Markov rockets home PPG for second of game
Jarome Iginla, RW
Based on players with similar statistics throughout history, Iginla may not bounce back from his NHL career-low of 27 points (14 goals, 13 assists) in 80 games with the Colorado Avalanche and Los Angeles Kings last season.
Consider Mike Modano. Late in his career, his scoring statistics closely matched Iginla's. At age 37 through 39, Modano had 57, 46 and 30 points; Iginla had 59, 47 and 27. At age 40, Modano scored 15 points (four goals, 11 assists) in 40 games for the Red Wings and then retired.
Though Iginla's days as a top-six scorer may already be behind him, like Modano, Iginla has valuable leadership qualities and can contribute grit from a depth line.
There are a lot of similarities between Doan and Iginla. They are 40, they scored 27 points last season, and they can provide leadership and grit. For most teams, choosing between them is more a question of chemistry and fit than underlying numbers.
If there's something that makes Doan stand out, it's that the Arizona Coyotes captain already made the successful transition to a secondary player who can help develop younger linemates. Doan spent the second half of last season on an effective secondary scoring line with rookies Christian Dvorak and Brendan Perlini. Dvorak was tied for 14th among NHL rookies with 33 points (15 goals, 18 assists) in 78 games and led the Coyotes at plus-7.
Brian Campbell, D
After more than a decade as an effective top-pair defenseman, Campbell transitioned into a secondary role last season with the Chicago Blackhawks. His ice time was reduced from 22:16 per game with the Panthers in 2015-16 to 18:25, and he averaged fewer than 1:00 killing penalties for the first time since 2009-10.
Campbell dropped from 31 points (six goals, 25 assists) in 82 games in 2015-16 to 17 points (five goals, 12 assists) in 80 games last season.
Like Doan, Campbell has demonstrated the ability to help develop younger players he is paired with, like Trevor van Riemsdyk last season, and Aaron Ekblad of the Panthers, who won the Calder Trophy in 2014-15.
Wherever Campbell plays, whatever his role, and whomever his partner, he finds a way to give his team an advantage. Over the past two seasons, his plus-43 is tied for seventh in the NHL.