JETS captain Nigel Boogaard will consult specialist Neil Halpin in search of answers after his nagging groin issue "flared up" at training.
Boogaard, who has missed the past three games, had been progressing well and was pushing for a return against Adelaide at Coopers Stadium on Sunday.
Instead, he is likely to have more scans and a longer stint on the sideline.
"The groin keeps flaring up and hasn't settled down yet," coach Ernie Merrick said. "We are looking at different options."
Boogaard, despite the setback, is expected to be named in an extended squad to travel to Adelaide.
"He is invaluable on the bench as a leader," Merrick said.
On the plus side, Kaine Sheppard trained fully on Tuesday for the first time since having a ligament in his big toe reattached in October.
"He did really well," Merrick said. "It was like he had never been away. We will play it safe with him but he will probably be right for the home game against Melbourne City."
Jason Hoffman had four chipped teeth repaired at the dentist after copping a ball to the face from Wanderers fullback Daniel Georgievski in the opening minute of the Jets' 2-0 win at home on Saturday night.
The veteran utility trained on Tuesday and is certain to play against the third-placed Reds.
Lachlan Jackson will again deputise for Boogaard in the city of churches.
The tall timber has been outstanding in a defence that has conceded just one goal in three games.
His inclusion has coincided with the return of enforcer Ben Kantarovski at the base of midfield.
While the Jets focus primarily on their attack, goalkeeping coach Chris Bowling was confident the defence would aim up again after consecutive clean sheets.
"Lachy has been waiting in the wings for a long time and has learnt a lot from Nigel and Nikolai Topor-Stanley," Bowling said. "Every time he has come in, you can see he has quality, whether it is with the ball or without it. He is only going to get better.
"With a central defender, their positioning and timing takes a bit of time to get there. He has stepped in and done a wonderful job.
"Ben Kantarovski coming back into the defensive midfield role with his experience and also having Nikolai Topor-Stanley and Mossy there - between them they have more than 700 games - is like having coaches on the field.
"As you go through the season, you get more comfortable with your combinations."
Bowling said the group's resilience had grown with every game.
"In games there are momentum shifts," he said. "We saw it in the second half on the weekend. It was backs-to-the-wall stuff at times but we didn't concede.
"Wanderers had a few chances but we either scrambled well or Mossy pulled off a great save. It's about being composed in those moments, getting through them and shifting momentum."
"The last 15 minutes we ran over the top of them."
After an injury-stalled build up to the campaign, Bowling said Moss was now "close to 100 per cent".
"He had a disrupted pre-season and it probably showed early on," he said. "You have to get that rhythm and he is absolutely firing now. That comes back to his application and his effort at training."