Pelle has been in fine form since moving to the south coast from Feyenoord in the close-season and his four Premier League goals brought reward with a call-up to Antonio Conte's Italy squad.
The 29-year-old scored the winner against Malta in Monday's Euro 2016 qualifier and returns to domestic action at St Mary's Stadium after netting a stunning overhead kick on his last run-out on home soil, a 2-1 triumph over QPR.
Gus Poyet's side picked up their first win of a league campaign that has yielded five draws from seven games when they beat Stoke City 3-1 at the start of the month, but Koeman is eager for Pelle to draw inspiration from his maiden outing on the international stage and help Southampton halt the visitors' revival.
Koeman said: "That gives him a lot of confidence, it's nice for him to have that debut for the national team. To score the winning goal was special for him.
"That was nice and we hope he will continue with that performance."
Pelle will have his work cut out against one of the top-flight's meanest defences, with Sunderland's tally of seven goals conceded bettered only by Saturday's hosts.
Southampton's excellent start to the season suffered a setback when they went down 1-0 at Tottenham in their final game before the international break, but Koeman's men still occupy a top-three spot.
That White Hart Lane loss was just their second in the league this term, but Koeman is well aware that Poyet's side will provide another stern examination of Southampton's credentials.
"It's not easy to beat them, they've lost once in seven [Premier League games] and it will be difficult," the Dutchman said. "It's difficult to beat them because they are well organised, strong in defence and it will be a tough game.
"They had five draws and that means a lot. That means sometimes they have problems scoring goals but they don't concede goals, which makes it difficult to beat them."
Poyet has been boosted by John O'Shea's decision to sign a two-year contract extension in the same week in which he scored a dramatic last-gasp equaliser for the Republic of Ireland against Germany.
The Uruguayan has a great deal of respect for Southampton and the way they have coped with the loss of several star names in the close-season.
"They lost many players and brought in new ones, who have adapted well," he told the club's official website.
"It's easier to adapt to a new league when you are winning and that's what they've been doing.
"They are an organised side who are difficult to beat; we need to be good and brave and play the game to our best. I think it will be a good game to watch."
Neither boss has any fresh injury concerns following the international fixtures, although Koeman still needs to assess Emmanuel Mayuka and Sadio Mane after they arrived back late.
