Gatland coached both men on last summer's Lions tour of New Zealand and says Wales must "attack them". However, it is his comments about Ireland's half-back pair which will garner the biggest headlines, coming a year after Sexton had to endure a head injury assessment injury against Wales in Cardiff.
'We have been pleased with how the forward pack has been going and how they have worked as a unit but as always there is pressure for them to perform too, ' added Gatland, who celebrates his 100th Test in charge of Wales this weekend.
Fullback Halfpenny, who scored two tries in Wales' opening Six Nations win against Scotland, missed the Twickenham defeat after picking up a foot injury.
He has plenty on his agenda before then, including a continued interest in this season's Six Nations title race, while the Ireland fixture also sees him up against a country he coached between 1998 and 2001.
"We've got to make sure we don't give Ireland an opportunity to kick to the sidelines by giving away penalties and execute their driving lineout, which is pretty effective, and allow Johnny Sexton to keep their scoreboard ticking over".
Ireland will go into the game leading the way after wins over France in Paris and Italy at the Aviva Stadium.
Despite losing that game, Gatland is bullish about his side's prospects and dismissed the notion that Ireland are the best team in the tournament.
"We've got to make sure we don't get caught up in that, keep our patience defensively and our discipline has to be good". They hadn't lost a home test since 2008 or 2009, and we beat them [in Wellington]. The way Wales played at home against Ireland previous year was outstanding, it was the model and benchmark. When we have been in tough situations, he knows how to get that extra couple of per cent out of you. "This weekend is about the performance and the result in a must-win game for us".
Wales: Halfpenny; L Williams, S Williams, Parkes, S Evans; Biggar, G Davies; R Evans, Owens, Lee, Hill, AW Jones, Shingler, Navidi, Moriarty.
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