The south-coast club are enjoying a magnificent season under Ronald Koeman and head to Suffolk on the back of a 1-0 win at Manchester United on Sunday.
Dusan Tadic scored the only goal of the game to give Southampton a first victory at Old Trafford for 27 years and move them third in the Premier League, firmly in the hunt for UEFA Champions League qualification.
However, a strong Southampton side, including Tadic, Morgan Schneiderlin and Graziano Pelle, were held 1-1 by Mick McCarthy's side in the tie's initial fixture.
And captain Fonte is keen to ensure his team-mates remain focused ahead of a challenging week that sees them visit Newcastle on Saturday after the meeting with one of the Championship's pacesetters at Portman Road.
"We won against Arsenal, drew with Chelsea and won at Manchester United," Fonte told Southampton's official website.
"We believe in ourselves, we know we have a great team, great staff and great manager. We just need to keep working.
"There's a long way to go. We go game by game. We have another tough game on Wednesday against Ipswich and then against Newcastle. It's a tough week."
Ipswich dropped to third in England's second tier following Saturday's 1-0 loss to promotion rivals Derby County, only their fourth defeat of the league campaign.
McCarthy will be without midfield trio Cole Skuse, Teddy Bishop and Jay Tabb due to illness, and expects to name a similar starting XI to the one that performed admirably at St Mary's Stadium.
"There's a virus going around the place that is laying one or two of them low," the manager said.
"I'm actually quite pleased because it knocked me low for about a week and I thought I was getting soft.
"It's made me realise I'm not as soft as I thought I was when younger, fitter people have been affected.
"Of course, I'm not really that happy that they are laid up because they can't play. It's very unlikely that they'll be involved, but I think the other 14 are okay.
"We seem to have a load of competition for places there [in midfield] – and yet it's there that we've had the majority of our problems, whether it be through injury or illness."
Southampton also have their fair share of absentees, with defender Toby Alderweireld unlikely to feature after picking up a hamstring injury at Old Trafford, joining Sadio Mane (calf) on the sidelines.
Striker Emmanuel Mayuka is on Africa Cup of Nations duty with Zambia, and Japanese defender Maya Yoshida is at the Asian Cup with Japan.
