The Norwegian has been used sparingly since picking up a foot injury against Borussia Dortmund in October.
He missed the games against Leicester City and Sevilla, and only appeared midway through the second-half of the 2-1 win over Fulham last weekend, scoring a dramatic late winner from the spot.
An unused substitute against Chelsea in midweek, Guardiola says he will wait and see how his top scorer feels before planning the team for Brentford.
Asked if Haaland would play against the Bees, the boss said: “We will see. After today's training, we will see.”
Then, asked if Haaland was better, Pep added: “A little bit.”
Kalvin Phillips and Kyle Walker were included in England’s 26-man squad for the World Cup on Thursday and Guardiola was asked for his thoughts on their selection – particularly as Walker is yet to start training after his September surgery.
Phillips made an impressive cameo against Chelsea on Wednesday evening, but Walker is still to return to full training.
“Kalvin you saw in the last game,” he said. “He is ready – Kyle, not yet.
“It’s a decision for Kyle and Southgate (the decision to select him) - 100% their decision. I am not involved.
“After Saturday, the players belong to the national teams. I am not worried.”