"I'm going to hold off on the testing; I'm a little dinged up," Tkachuk said. "There's no point in doing any of the bike tests or the testing right now if I'm not 100 percent. Whichever team drafts me, I'll be excited to test at development camp and see where I rank. We'll see what they think and go from there."
Tkachuk took his medical exam Wednesday and completed the functional movement screen test on Thursday, but will remain off his ankle as much as possible.
On Friday, prospects will take turns on the grueling VO2 Max bike test at HarborCenter. The VO2 Max, one of three tests on Friday, measures the endurance capability of a player's heart, lungs and muscles.
The Wingate Cycle Ergometer peak power output test, a 30-second all-out sprint on a stationary bike that measures a player's explosiveness and could provide critical information in learning how quickly a player might be able to begin a transition up ice, is the last of nine fitness tests to be completed on Saturday at HarborCenter.
Last year, center Jack Eichel, chosen No. 2 by the Buffalo Sabres in the 2015 NHL Draft, exhibited more endurance than Edmonton Oilers center Connor McDavid in the VO2. McDavid, chosen No. 1 in the 2015 draft, lasted 0.7 seconds longer than Eichel in the Wingate.
"I'm watching the facial expressions, the drive they have," Dallas Stars director of amateur scouting Joe McDonnell said. "Obviously, they're going to improve all those skills down the road once they get older and more mature, since the body changes. One thing you can see on the bike is the don't-quit-attitude type thing. Are they going to push it right to the max? You can see that in their face."
The top prospects this year are looking forward to the challenge.
"Oh yeah, there's always stories about the VO2 or the Wingate test," said Cape Breton left wing Pierre-Luc Dubois, No. 1 on NHL Central Scouting's final ranking of North American skaters. "It's going to be fun. I know a lot of the guys there."
Here are four other intriguing takes from Thursday at the combine:
1. First-round feedback: Center German Rubstov (6-foot-2, 178 pounds) grew up playing for Russkie Vityazi Chekhov, the same Russian minor hockey league program as Chicago Blackhawks left wing and 2016 Calder Trophy finalist Artemi Panarin.
The difference is Rubstov is three inches taller and will be selected in the NHL draft. Panarin went undrafted and signed a two-year contract with the Blackhawks on May 1, 2015.
"I like to play fast, but I do consider myself a defensive-center," Rubstov said through an interpreter. Rubstov, No. 5 on NHL Central Scouting's final ranking of international skaters, is no secret at the combine this week; he had 26 interviews scheduled with NHL teams.
Rubstov began playing hockey in Chekhov when he was 4 years old.
"I like Panarin because he's very technical and fast, can beat anybody on the ice and he can score," Rubstov said. "I'll need to work a little more to be as fast as he is right now, though. But I feel I've done enough this season to hopefully be drafted in the top 15."