De Bruyne's season has been wrecked by a pair of medial knee ligament injuries but on Boxing Day he made his first start of the 2018-19 Premier League campaign in a defeat to Leicester City.
City's chances of chasing down Liverpool would be much improved were De Bruyne available, but Guardiola is unsure whether the midfielder will make his squad.
"He trained today but we need to check in the morning," Guardiola said. "He is much better."
Finally. pic.twitter.com/18TucrDrgE— Kevin De Bruyne (@DeBruyneKev) December 15, 2018
Thursday's match is likely to be pivotal in the title race with Liverpool having the chance to stretch their advantage over City to a double-digit lead.
City can narrow the gap to a more manageable four points with a victory, though, and Guardiola is determined to stay positive despite Liverpool's form.
"Our reality is clear, we have seven points down, so it will be the second game of the second leg [of the season], a lot of points to play [for]," he told a press conference on Wednesday.
"It's a big opportunity for us to reduce the gap but our focus is the same. Everyone is asking if we lose - if we lose, we lose. But we are going to try to make our game, win it and fight as far as possible for our chance to win the Premier League.
"Listen, I cannot figure out or imagine what happened in the past will happen in the future. Winning games in the past doesn't mean it will happen in the future. I have the feeling we can beat everybody, but everybody can beat us. We beat them 5-0 here, but last season.
"It's Liverpool, my friends, along with [Manchester] United the best team in England in history. Of course, they can beat us but, of course, we can beat them. It is what it is. They're in top form. They are in that moment the best team in Europe with consistency and controlling details but it is a chance for us to reduce the gap.
"Focus on what we can do to win the game. People keep asking what happens if we lose, but what happens if we win? After, we analyse, and three days later the FA Cup, then EFL Cup, then Wolves, and at the end of the season we'll see."
Despite City lagging behind Liverpool due to back-to-back losses against Crystal Palace and Leicester, Guardiola insists he is happy with his side's title defence so far.
"I am so glad, I am delighted, we have a lot of points," he continued. "We dropped some at home we didn't expect against Crystal Palace but they were so precise, three shots on target and three goals.
"But one team has been better, we have to congratulate them. I know what happens when you win with 100 points, nice words from everybody, but how hard it is to come back [and do it again]. But we did it. And I'm delighted with the players, staff, everybody."