Joseph described one of his key backs as a ''heck of a loss'' when he yesterday revealed Ellison had undergone shoulder surgery just before Christmas.
In a double blow, the Highlanders backline will also have to do without rookie winger Declan O'Donnell, also with a shoulder complaint.
Ellison (29) will be out for five to six months, which once would have been season-ending but now, with the expansion of the competition, means there is a good chance he will be available should the Highlanders break their playoff drought.
Joseph said the experienced second five-eighth initially hurt his shoulder playing for Otago against Counties-Manukau in the ITM Cup.
''Then he went on the All Black tour and soldiered through, which says something about the character and strength of the bloke.
''They didn't know how serious it was at that stage. Tamati was confident he'd be right but it started to get really painful.''
A scan on his return to New Zealand revealed a dislocation and a break at the top of the shoulder bone, Joseph said. Surgery was the only sensible option.
''We had to make that decision. Far better to get it done. We didn't want to get Tamati into the pre-season, then realise he was no good, then lose him for the whole year.
''In fact, the surgeon was very clear that Tamati wouldn't have lasted a couple of days, let alone a couple of months.''
The Highlanders are relatively deep in the midfield, so will not look to replace Ellison.
All Black Ma'a Nonu is joining the side, Shaun Treeby and Phil Burleigh are proven at this level, and rising star Jason Emery will be eager for game time.
It seems likely, however, Joseph will find a replacement for O'Donnell.
The Waikato and New Zealand sevens player has just learned of the extent of his own shoulder dislocation and is to have surgery this week.
There is little cover on the wing so the Highlanders will probably seek a permanent replacement. Exciting Otago outside back Tony Ensor is in the wider squad and could be an option.
Injuries are common in top rugby - Joseph knows that as well as anyone - and the coach is not stressing about the situation.
''You can't worry too much about it because you can't do anything for it,'' he said.
''A year ago, we didn't even have Tamati Ellison. But he was a stand-out player for us when he came back from Japan and he is a huge loss.
''But we'll soldier on. The next guy will step up.''
Highlanders first five Colin Slade was progressing well after his long injury break and was ''bouncing around like he used to,'' Joseph said.