Klopp denies idea that quick returns have caused Liverpool injuries
Alexander-Arnold will miss the League Cup final against Chelsea later this month because of a knee problem that recurred in last week's win over Burnley for the Premier League leaders.
Thiago faces another spell on the sidelines after picking up an injury following an appearance as a late substitute in the defeat against Arsenal, while Szoboszlai has hurt his hamstring again.
"I got the news that there was a discussion we might have forced Trent back," Liverpool manager Klopp said on Friday.
"He had two setbacks and it is really unfortunate, no one wants that.
"But different cases, different scenarios and as long as I'm here we never forced anyone back and we will never do.
"We work in a high-performance area and if you have the same injury you are fit after three days and another guy after four weeks."
Klopp, whose team travel to Brentford on Saturday, said the players had been ready when they were passed fit to play.
"We can never know if it would have happened anyway or whether it was something before," he added. "Very unlucky and unfortunate.
"It is not great but it says nothing about the quality of anyone. The world we are living in is always immediately, 'Medical department? I'm not sure about that', but it is nothing to do with that.
"We have to bring the boys as back as soon as possible but never sooner than they are ready from our point of view."
In brighter news for Klopp, top scorer Mohamed Salah returned to training this week after a month out with a hamstring problem sustained on Africa Cup of Nations duty with Egypt.
"Mo is back in full training, that brings him automatically in contention of course," said the Liverpool boss.
The German also welcomed the "really nice" announcement that former England boss Sven-Goran Eriksson will be part of the management team for a charity legends game against Ajax at Anfield next month.
Eriksson revealed in January he had "best case a year" to live after being diagnosed with pancreatic cancer.
The 76-year-old Swede disclosed at the time his lifelong love for Liverpool and how he had always wished to be manager of the club.
"I was always convinced that it will work out some way, and then this is now really nice," said Klopp. "A legend coaches legends, so it's really cool."
