The player knew himself that had he passed rather than shot when played clean through on goal just before the break, the Reds would have won the game.
"I saw in Sadio’s eyes that if he could turn the clock back, he would do it," Klopp admitted after the game at Anfield on December 10.
Unfortunately for Mane, he's taken the wrong option several times this season, prompting many frustrated fans to ask what's happened to the player who enjoyed such a sensational debut campaign at Anfield.
There have still been moments of magic. As Klopp acknowledged after Mane had netted in the 2-1 win at Burnley on New Year's Day, "He scored a fantastic goal but it was not a world-class game of Sadio."
The 25-year-old has struggled to play at his usual consistently high level and, consequently, there has been a noticeable drop in his efficiency. He has already taken more shots than he did during his entire 2016-17 Premier League campaign yet he has only scored six goals, seven fewer goals than last term.
Whereas last year, Mane carried the Liverpool attack; this season, they have too often had to carry him.
Liverpool's talisman has now become a member of Mohamed Salah's supporting cast, prompting the likes of Ian Wright to suggest that Mane has been transformed into a green-eyed monster, jealous of his fellow African, who has become the darling of the Kop after a sensational return of 22 goals in just 26 Premier League appearances since joining from Roma last summer.
Such an opinion rather conveniently overlooks the fact that the pair are very close. Indeed, both have admitted that they regard the other as their best friend at Anfield.
When Mane got injured playing for Senegal earlier this season, Salah was among the first to get in touch. "Mo is the perfect gentleman," Mane said. Salah says the same of Mane but then, everyone does.
As so wonderfully detailed in an exclusive interview with Goal earlier this season , he is not the stereotypical footballer. He is no way egotistical. Moreover, he really cares.
The flip side to that is that is he takes things to heart: defeats, missed opportunities, poor performances. “If I have an injury or we have disappointment with a result, the only thing in my head is about the reaction,” Mane explained.
Essentially, all he ever wants to do after a setback is make amends, which would explain why he was so frustrated at only being afforded a minute of game time in Liverpool's Premier League meeting with Chelsea in November.
When Mane and Klopp engaged in a heated discussion at the end of the game, it was used as evidence that the pair's relationship was strained. Both immediately insisted otherwise, explaining that the discussion had been over Mane's positioning.
Being moved from the right wing to the left following Salah's arrival on Merseyside has been touted as another reason for his struggles this season but the player himself insists he feels at home anywhere along the front line.
Admittedly, he has also been given greater defensive responsibilities this season – he has already made 20 tackles in 19 outings this season; he racked up just 23 in 27 appearances last term – in order to give new signing Salah greater freedom but the notion that he is upset with how Klopp is utilising him is also at odds with reality.
Indeed, it is Klopp who has done the most to help Mane to stop being so hard on himself.
“Of course, we had talks," the German said of the former Southampton star's struggles. "I cannot tell you what I told the player in a one-to-one meeting, but it was about what he did so far.
“One or two things not that good, but the rest good. So, let’s build on that and ignore the rest. That is how life is.
“You cannot think all the time about your mistakes because that makes no sense. You cannot forget all the good things. We are all a bit like that and sometimes people need help to realise again the good situation.
“He is in a fantastic situation where everyone loves him in the club. But he played from [the heart] and not from [the head] and nothing really worked out in the end.
“I like to be honest and I don’t want to say Sadio was brilliant when he wasn’t. Everyone could see that he struggled a bit."
The stop-start nature of his campaign hasn't helped. He opened the season with a goal in his first three games before getting sent off against Manchester City, which resulted in a two-game suspension.
He returned to face Newcastle at the start of October only to then immediately pick up a hamstring injury while on international duty. Since then, it has seemed as if he is trying too hard to make up for lost time; to keep up with the remarkable goalscoring exploits of Salah, and also Roberto Firmino, who is enjoying the most prolific campaign of his Anfield career.
Klopp was enthused by Mane's goal in the dramatic 4-3 win over Manchester City but he has performed erratically in the five games which have followed. Too often, he is shooting when he should pass. Sunday's performance at Southampton was another case in point: too desperate to join his fellow forwards on the scoresheet, he butchered three goalscoring opportunities.
He still contributed to the win, as Klopp was at pains to point out afterwards, but he was once again nowhere near as effective as either Salah or Roberto Firmino.
The Liverpool boss is quite right when he says, "Sadio on an average day is still a fantastic player." He's shown that in flashes this season.
Not that he needs to be told that of course. He already knows it himself.