Since then Southampton have won seven games as the Austrian manager lifted the south coast club out of the relegation zone and into 16th place with the help of youngsters and academy graduates who were handed their Premier League debuts.
"I have to say the job he (Hasenhuettl) is doing there is incredible," Klopp told reporters. "He brought young players in, academy players, a pretty brave decision.
"We have to see the time Ralph Hasenhuettl is in at Southampton. I think they are eighth in the form table, last 15 games at least. The games they lost, they were unlucky rather than playing bad.
"So that means they are fighting for the league, and that gives you good information about the intensity of the game probably. It's a home game for Southampton, and they play a clear style of football."
Liverpool defender Virgil van Dijk was a doubt for Friday's game after an ankle injury in the 2-1 win over Tottenham Hotspur on Sunday but Klopp said he trained normally and would be available to take on his former club.
The Dutch defender has been instrumental in Liverpool having the best defensive record in the league this season and Klopp hailed his impact at the Merseyside club.
"He's so important to us, not only as a player but as a person," Klopp added. "I couldn't say a bad word about him even if I wanted.
"He has improved us and he has improved since he came here as well. He's a different player to when he was at Southampton. (Playing in the) Champions League quarter-finals, semi-finals and final help you as a player."
Klopp also said he was not concerned by Mohamed Salah's goal drought. The Egyptian forward has not scored since the start of February, a run of eight games in all competitions.
"People talk about how many games he hasn't scored in but he doesn't seem bothered," Klopp said. "It's about work rate, doing it again and again, and one day the ball will bounce in your direction.
"We have 79 points. You can't have that if you have major problems in a season."
(Reporting by Rohith Nair in Bengaluru, editing by Pritha Sarkar)
