Liverpool have made an inconsistent start to the Premier League season under Iraola, with his side drawing three of their opening four league matches despite a Champions League victory over Atletico Madrid, and the Spaniard said managing workloads remains a key challenge.
"There are players who play every three days with no issues. They are very robust, their performances don't change too much," Iraola told reporters on Monday.
"There are other players where the risk is bigger and the performances are different. I have to learn who is ready to play games every three days and who needs a rest so their performance level isn't affected."
The Liverpool manager said experienced players such as captain Virgil van Dijk had already shown they could handle the demanding schedule, but assessing younger players and recent arrivals would take more time.
"We have some other players, experienced, have done it, I know they can do it," Iraola said. "Virgil can do it, because he has done it before, he has the experience and his performance isn't so affected.
"With the younger ones and those coming from abroad, there are some question marks, for them and for me and everyone. We will have to study it case by case."
Iraola also hinted at changes for Tuesday's cup tie against Spurs, with summer signing Giorgi Mamardashvili set to be handed his Liverpool debut in goal ahead of first-choice keeper Alisson Becker.
"I think there are few doubts with Becker, he's playing very well," Iraola said. "I rate Giorgi very highly, I know him from Spain. We tried to sign him for Bournemouth before I came here. For me, he's a very good keeper and he's going to start tomorrow."
On the injury front, Iraola said defender Joe Gomez had returned to training and will be available for selection, while Conor Bradley remains sidelined.