The Premier League champions progressed all the way to their first ever final in last season's competition, losing by a narrow 1-0 scoreline to Chelsea in May.
City, who have also been drawn in Group A alongside Paris Saint-Germain and Club Brugge, are now preparing for their very first meeting against Leipzig.
Speaking to the press ahead of tomorrow's game, Guardiola has praised the German club's philosophy and style of play.
"Leipzig are always complicated. What we have seen from them, the philosophy of their club, the Red Bull philosophy with young, dynamic players who play narrow in all sense. It is so important to start well, especially at home," Guardiola said.
The Catalan coach has also given his thoughts on the Champions League group stage as a whole, suggesting that the competition is "unpredictable" and has become much stronger since he began his coaching career with Barcelona.
"When I start this competition every season [I am asked] about being the favourites and I cannot answer you because I don't know," he said. "It is unpredictable, there are many strong teams. It is completely different to when I started with Barcelona. The group stage is difficult."
City's first Champions League fixture against Leipzig this week is followed by an away trip to Paris at the end of this month, before another match on the road in Brugge on October 19.