Doak missed three games for Liverpool after picking up an injury on duty with Scotland U21s, but was back on the bench for the 1-1 draw at Luton.
If that fixture had played out differently, the likelihood is that he would have been brought on, but his return to the side is now due to come vs. Toulouse.
A 23-man squad flew to France on Wednesday – including the late addition of Kaide Gordon – with Klopp later telling reporters to expect changes.
The opportunity to rest Mohamed Salah cannot be passed up, and in his pre-match press conference, the manager described Doak’s availability as “really helpful.”
“Obviously Ben really showed up for us, had a really good pre-season, had minutes with us, had a real impact,” Klopp said.
“That is always for a boy not too cool, it cost a bit of rhythm.
“Now he’s back with us fully in training, so he’s an option for [Thursday] which is really, really helpful for us.
“Because as I said, we have to make changes, but we want to make changes with quality. Ben has obvious quality, so that’s why it’s really helpful.”
Klopp made 11 changes for the Europa League opener at LASK, nine for the visit of Union SG to Anfield and then eight for the reverse fixture against Toulouse last month.
He will take a similar approach on Thursday, though with fewer options available to him there could still be a number of key players starting.
“We had already a lot of games this season, so if we would have played the same team all the time, that’s not possible,” Klopp continued.
“So we could make the changes, we made the changes, we will make changes.
“I don’t know exactly how many [vs. Toulouse], you have to count. But it will be a few probably. It will be a strong team, and that’s all I need, and then we go for it.
“There’s nothing to do with that we put more emphasis on this competition or [another], that’s not the case.
“We just want to win football games and for that you need fresh legs.
“If we can give that to the team, then we do that – fresh legs with quality, obviously – and that will be the same [on Thursday].”