Back-to-back defeats to England and Scotland have put Rob Howley’s men out of contention for the title, with games against Joe Schmidt’s side and France to come.
The loss at Murrayfield saw Wales rightly criticised for a poor second half display in which they failed to score a point.
Howley’s side also have a bigger picture to look at because if they lose their next two games, they will drop out of the world’s top eight and face a nightmare pool stage draw for the 2019 World Cup.
That will be in the back of Welsh minds, with the squad desperate to prove a point to their critics.
Biggar told The Rugby Paper: “We’re presented with another challenge against a top, top team.
“Ireland were stunned at Murrayfield on the opening weekend, but they’ve been on a roll since then and this is a must-win game for them if they want to win the title.
“We know we’ve got two huge games now to show we are better than we produced in Scotland last weekend.
“So motivation is not very difficult. You are playing for Wales and putting on the red jersey which means a heck of a lot. For me it’s a boyhood dream so it is not particularly difficult running out at the Principality Stadium in front of 75,000 people against a very good side.”
Biggar was left hurt by the accusation he overruled captain Alun-Wyn Jones in kicking to the corner against Scotland, but knows Wales must retain the ball for longer periods if they are to have success.
Failure to do that against Ireland is likely to result in a third straight defeat.
“We’re not hiding behind the fact we’ve spilled a lot of ball and made a lot of errors,” Biggar said.
“The bottom line is we could not keep enough phases going to exert the pressure on Scotland. It is not a mentality issue, but there is no doubt we did not keep hold of the ball to force penalties and create more try-scoring opportunities.
“It is not about feeling sorry for ourselves and sulking in the corner. It is about fronting up and making sure we are better for Ireland.”
While Wales have faced criticism, Biggar has had a solid Six Nations at No.10. He is set to start his fourth game of the tournament and go head-to-head with Johnny Sexton, right.
The pair have faced each other on four occasions, with Wales coming out on top twice and last year’s encounter ending 16-16 in Dublin.
Biggar added: “Johnny is world-class. He is going to be a hugely difficult opponent and he runs the show for Ireland.
“I’ve always said that whenever you play against Johnny, if you are not 100 per cent on your game it will be a difficult afternoon. It’s up to us to make his life as difficult as possible.”