The pair have been named on the bench for the vital first-leg clash of the Champions League semi-final at Camp Nou, as the Reds look to reach the final for the second successive year.
The absence of Firmino and Alexander-Arnold, two stand-outs at Anfield this year, has already alarmed some fans, but Klopp has now moved to allay fears that both may play no part.
Speaking to BT Sport pre-match, the 51-year-old stated that his decision to bench the pair - along with club captain, Jordan Henderson, came down to fitness and minutes, given Liverpool’s hectic end-of-season schedule.
“That’s how it is with the short periods between the games,” Klopp stated. “You cannot be sure.
“Bobby wants to [play] and the medical department told me ‘yes, it’s good’ but then you have to make sure – I’m not sure if 90 minutes or whatever.
“So he doesn’t have to start, that’s why we start like we start. Bobby is on the bench, that’s good news.”
“The boys are all in good shape. [But] Hendo played five games in a row, for example, and we play on Saturday and Tuesday.
“Millie [James Milner] didn’t play for two games so it was clear we had to use him. Fabinho didn’t play for two games so it was clear we had to use him. Naby [Keita] didn’t have that many games during the whole season, Gini [Wijnaldum] didn’t play all the games.
“That’s why midfield, where it’s really intense, is where we have to make sure we have legs there.
“It’s the same for Trent; it was clear when Joe [Gomez] would be available again that there would be a game and I think today it makes absolute sense in that position.
“For Trent it’s good, he can refresh a little bit, there are important games to come. But the first thing we wanted to make was a good line-up for tonight and for a good line-up you need legs and that’s what we tried to make sure.”