Back in the Socceroos set-up after a long lay-off due to a knee reconstruction, Kruse sent shockwaves through the camp when he went down clutching his knee during the session.
The 25 year old appeared to slip and fall awkwardly as he was about to receive a pass from Tommy Oar.
After staying down for several minutes, Kruse eventually got to his feet and left the session immediately, although Australia's medical staff is confident the injury has nothing to do with his ACL problem.
It's still unclear if the problem will rule Kruse out for Belgium and then Saudi Arabia in London four days later.
Rubbed out of the FIFA World Cup after cruciate ligament surgery nearly eight months ago and without a competitive start for club or country since January, Kruse, 25, is aiming to relight the fire which saw him glow as Australia's brightest new talent before he was struck down.
Prior to the injury scare, Kruse was adamant he is ready to start against Belgium, insisting: "I have the full clearance from the surgeon and the physios and doctors and I am ready to play.
"If I start I will be buzzing. I am not expecting miracle performances immediately, though it would be great if it happened.
"Hopefully, I can get 60 or 70 minutes. The message from my club has been that if I get some game time for Australia I will hopefully be back in the Bayer squad when I return.
"I was back in training within six months (following surgery) and for a cruciate ligament that's quite quick, especially since I did the meniscus as well.
"It’s normally a nine month turnaround, so to be back in training with the first team is something I am proud of.
"I have played three or four pre-season games but I haven't featured so far this season.”
Kruse had the option to seek regular game time elsewhere by going out on loan, but - after consulting with coach Roger Schmidt - opted to remain with Bayer.
"We talked about it, and he wanted me to stay and I was happy to do that," he added.
"There was the opportunity to be loaned out, but it wasn't that simple, and now I want to get some game time with Australia and then go back to Germany and hopefully be a part of the squad.
"When you miss so long through injury you just really appreciate what football means to you."
Kruse said he harboured no fears or inhibitions in trusting the handiwork of the surgeon as he seeks to make up for lost time.
"It (the injury) can play on your mind if you cop little knocks, and while you may initially panic, that doesn't last long," he said.
"I am just excited at the thought of pulling on the green and gold again, and I think this whole time out has made me mentally stronger."
Kruse, who has 28 caps, was on the cusp of being a regular starter with Bayer when he suffered the injury - and having missed the World Cup he is now focused on playing his part in winning the Asian Cup on home soil next January.
"That’s my big goal now," he said. "We should be looking to win it and if we do that it will go a long way to making up for me missing the World Cup.
"We have never won anything and there's no better chance than this. We have a great young squad and everybody is fighting for positions.
"The boss has installed the belief in the players and the public has started to jump on board too with the way we are trying to play."
He is expecting further progress against a Belgium side without star names Eden Hazard and Romelu Lukaku, adding: "I think we will do well, even though everybody knows how good they are - no matter who they pick."