Man City's De Bruyne, Laporte and Stones to miss first leg of Leipzig tie
The City manager said in Tuesday's pre-match press conference De Bruyne and Laporte were both sick and could not be included.
"Kevin and Laporte - illness," said Guardiola.
"It is what it is during the season unfortunately. Sometimes something happens.
"Kevin didn't feel good right after the game against Nottingham on Sunday and yesterday Laporte didn't feel good, so they're not going to play."
Also on Tuesday, Leipzig coach Marco Rose said City still posed a major threat despite the 31-year-old De Bruyne's absence.
"I think Kevin is among the best players in the world. He sees space, he knows space and he's dangerous in front of goal" Rose told reporters
"A lot goes through him in this team, but he will be replaced by someone world-class.
"Man City work as a team. They are not individuals. A team will be on the field tomorrow, a team which wants to win the Champions League," he added.
Leipzig said Spanish midfielder Dani Olmo would miss the match while France forward Christopher Nkunku was in doubt and would, at best, start from the bench.
Guardiola said on Tuesday he hoped Nkunku would be fit enough to play for the Germans, saying "it was a pity that he missed the World Cup."
"Top-class player, we saw last season at home.
"Hopefully he'll be back in Manchester. Always I want to play with the best players in the top sides."