Coutinho completed his long-rumoured move to Barcelona on 6 January for a reported fee of £142m ($192m) as Liverpool lost the services of one of their key players.
Jurgen Klopp's men will now host league leaders City on Sunday, 14 January, in what will be their first league game without the Brazilian.
However, Guardiola believes despite losing a "top player" in Coutinho, Liverpool are more than capable of remaining a threat and will adequately replace the 25-year-old.
"I think Barcelona have signed a top player who suits perfectly the way they have wanted to play for the last 20 years," Guardiola said, as per the Mirror.
"But Liverpool now have resources and they will go to the market. Jurgen knows exactly what he needs to do for his team and they remain a top, top team.
"They have already played a lot of games this season without Coutinho because of injuries and other reasons. And they were always a good, stable team, so this is not going to change my opinion about Liverpool."
Liverpool are looking to the likes of Riyad Mahrez and Thomas Lemar as potential replacements, with the most recent reports stating that they have opened talks with the former over a move.
The Reds are also interested in the possibility of bringing Naby Keita to Anfield early and are reportedly ready to pay an additional €20m (£16m, $24.4m) for the Guinean midfielder, who already has an agreement in place for the summer.
Meanwhile, Guardiola is not letting his side's tremendous form get into his head. With 20 wins and two draws in their 22 league games so far, City are on course for the Premier League title and even a potential unbeaten season.
However, the Spaniard is simply taking things game by game and is focused on the club's visit to Anfield next.
"I will be judged depending on results and what happens," Guardiola added. "But I am not thinking about how many games are left to win the championship or how many games to make a big crash.
"I have never said to the players that we need to win seven, eight, nine, 10 games to be champions or have to drop so many games not to be champions.
"My focus is Liverpool. What they do, what we are and what we have to do to beat them."