Back-to-back Premiership defeats have seen Exiles slip down to eighth in the table, six points behind Leicester Tigers in the final play-off spot.
Saints, on the other hand, have won four of their last five league matches and head the chasing pack behind Harlequins and Saracens.
Not only that, but Northampton's last two league visits to the Madejski have seen them emerge victorious - by scorelines of 31-7 and 26-20.
Joseph, though, believes his side can halt the hat-trick bid and bounce back from their disappointing defeat to Newcastle Falcons.
"It's a massive game for us," he told the Chronicle. "We've had a bad run of late and we've to get back to winning ways.
"We want to make a statement on Sunday. It was bitterly disappointing to lose at Newcastle and now we have to look ahead and do our best to get a result against Saints.
"They're a strong side with a good squad but so are we and we will need to make sure we match them all over the pitch."
When the two sides met earlier in the season it was Irish who came out on top 14-13 thanks to a late penalty from Tom Homer.
The full-back is just one of a number of young players at the club who have impressed this season, including 20-year-old Joseph.
Despite losing a couple of months to injury, Joseph has come back stronger and head coach Toby Booth admitted recently that it's a matter of when, not if, he is called up for the England senior side.
As well as being selected in the Saxons squad, the pacey winger has been nominated for the LV= Breakthrough Player Award and says he is delighted with the way the season has panned out.
"It's a great honour to be nominated for the LV= award, a lot of good young players have been chosen as well and I'm thrilled to be amongst them," he commented.
"I'm really pleased with the way the year has gone in general, I started it really well but then I had the injury and I've come back from that. I'm glad to be playing again for the first team and now I want to help the club finish in the top four and challenge for silverware, which I think is possible."
Both Irish and Saints will be without players on international duty for the clash on Sunday, including Alex Corbisiero and Chris Ashton.
But although the make-up of the squads will be altered by the Six Nations, Joseph says it is not a problem.
"Players are now away at the Six Nations but that is to be expected and we have to adapt," he said.
To vote for your LV= Breakthrough Player, and for details on how to purchase tickets for the LV= Cup final on March 18, visit www.lv.com/rugby";. Voting closes at midnight on March 11th. The winner will be announced on March 13th.
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