He is expected to be out of action until January, which is a serious blow for the province as Ta'auso has been ever-present for Connacht this season, starting their first seven competitive games.
Flanker Ray Ofisa fractured his cheekbone in last weekend's league tie at Stadio di Monigo, and is facing a lay-off of six to eight weeks.
Ofisa, who was troubled by vertigo towards the end of last season, is still in hospital under observation in Italy.
Meanwhile, the focus for Eric Elwood's men now switches to the visit of the Samoan national squad next Tuesday. The friendly match at the Sportsground will be televised live on RTE Two (kick-off 7.05pm).
Commenting on the clash with the South Sea Islanders, Connacht Rugby CEO Gerry Kelly said: "We are delighted to have a fixture of this calibre at the Sportsground, it continues a tradition of national teams visiting the west.
"Portugal played here the year before last and South Africa played here in 2007, the year they went onto win the World Cup, so we are well used to hosting teams from other nations.
"Season tickets will be valid for this match and we are hoping that the midweek fixture will enable plenty of people who cannot make weekend games to attend."
Connacht Rugby has a long association with Samoa. Gavin Willams and Ofisa Treveranus have both been capped by the Samoan national side having played with Connacht, while Ray Ofisa and Niva Ta'auso, members of the current Connacht squad, also hail from Samoa.
Samoa will play Ireland, England and Scotland before returning to play a one-off Test match against Japan as part of their end of year tour of the Northern Hemisphere.
Connacht head coach Eric Elwood commented: "It's great to get big exciting fixtures like the Samoa game at the Sportsground, we've played New Zealand, South Africa, Fiji in the past and Samoa have now moved up the international rankings, it's an exciting challenge for us.
"We will be making some changes to our team because some of our senior players will need a rest, but it's a huge opportunity for some of the younger players to display their skills against international players.
"One thing for sure when you play Samoa is that it'll be a physical encounter and there'll be some big hits next Tuesday, but we're hoping that some of our players will be able to show their wares in attack.
"It's a great opportunity for them to show what they can do and to challenge for places in the team against the Ospreys and Edinburgh which are coming up in the Magners League."
With 4,582 spectators having packed into the Sportsground for the recent derby match against Leinster, Elwood is hoping another big crowd turns out at the Galway venue next Tuesday.
"The Sportsground crowd have been excellent this year, we've had great support in our home games to date, we're very happy that people are making the effort to come down," he added.
"As I've said before, they really do make a huge difference to the squad. They give the guys a lift and we just want them to keep supporting us especially now heading into the winter months when it can be a bit more difficult weather-wise."