Slade has endured a horror injury run since joining the franchise two years ago.
He picked up two broken jaws in the 2011 season which ruined his year.
He had a slow start to last season thanks to a nagging groin problem, which ruined his World Cup, and he also had to have a hernia operation.
He struggled to find full match fitness early on but seemed to be getting up to speed before he broke a leg against the Brumbies in late March in Canberra.
Straight after the incident there were doubts whether Slade would get back and front for a full year in the 2013 season.
However, he had expressed confidence in making a return for Canterbury towards the end of the ITM Cup.
That has not happened but Highlanders coach Jamie Joseph said Slade had just started training again.
"He's still got five months to go until the start of the season and five months is a long time in rugby. We'll just see how he goes along the way," Joseph said.
The Highlanders have a back-up in Lima Sopoaga, who himself has suffered injury problems. A broken shoulder ended his season early this year.
He has come back and played for Wellington in the past few games but is still far from proven at the Super 15 level.
Otago first five-eighth Hayden Parker is expected to pen a deal with the Highlanders who will have an expanded 35-man squad for next year.
Joseph said Adam Thomson had told him at the end of last season if he stayed in New Zealand he would play for the Highlanders.
Thomson has yet to make a commitment to play in New Zealand next year and was linked with a move to Japan.
However, no firm decision has been made by the Otago loose forward, who is in camp with the All Blacks. He was linked with a move to the Blues but may be thinking twice about that as the Auckland-based side loses players.
Joseph has not yet shut the door on Thomson (30) but appears to be running out of patience with the rangy loose forward, who has had a stand-out couple of years with the franchise.
"He is yet to make a commitment to New Zealand rugby and that puts franchises under incredible pressure in terms of building their squads.
"We talked at the end of the season and he said he would come back here.
"He seems to have changed his mind but his phone has gone off.
"I've got to keep running. My job is preparing the side for next season."
He would be prepared to have Thomson back if the blindside flanker was keen but Joseph said places were filling up fast.
The Highlanders are set to finalise the first 28 players in the squad by the middle of next week and will name their full squad by the end of the month.
