Usually when players decline it is a process so slow that at first it is almost imperceptible: a fraction slow to react here, slightly late to a challenge there, occasionally outmuscled or outpaced in a way they never used to be. Sometimes it is to do with age, sometimes with injury, sometimes form and confidence is eroded and never returns. With Kolo Touré, though, you can pinpoint the moment of crisis absolutely.

He stopped being a top-class defender 22 minutes into the second half of Ivory Coast's Africa Cup of Nations semi-final against Egypt in Kumasi on 7 February 2008. Abdul Kader Keïta had just pulled a goal back so the Ivorians trailed 2-1 when Egypt's goalkeeper Essam El-Hadary launched a long clearance downfield. Abdoulaye Méïté challenged with Emad Moteab and the ball glanced off his shoulder for Amr Zaki, about 25 yards out, with Touré between him and the goal. Zaki took the ball on his right foot and looked to cut back inside on to his left foot. Touré, backtracking, followed the turn inside and took three steps before realising that Zaki had barely moved. The ball had got caught under the foot of the then Zamalek striker who, seeing Touré had effectively run away from him, drove on with his right foot and hit a low shot into the bottom corner. Mohamed Aboutreika added another in the final minute and Egypt won 4-1.

It was the third goal, though, that lives in the memory. What on earth had Touré been doing? Yes, Méïté's misjudgment had put him in an awkward position but he seemed to have recovered. Why, in that situation, would he run two or three yards away from the ball? Why invite Zaki into the box? The answer, perhaps, is that Touré had been carried off on a stretcher during the group stage with a groin injury. Had he, perhaps, come back too soon? Did he, realising he wasn't fully mobile, try to anticipate Zaki's movement to prevent himself having to stretch?

It is easy to forget how good Touré was before that incident. He had started as a right-back at Arsenal before moving into the centre on a regular basis in 2005. He was quick, read the game well and radiated authority. When Sol Campbell left a game against West Ham at half-time in February 2006, Touré, who was at the Cup of Nations in Egypt, spoke eloquently and sympathetically about his defensive partner. He seemed a natural leader, tough but empathetic, and when Arsenal reached the Champions League final later that season, the main reason was the form of Touré and Philippe Senderos in a record run of 10 consecutive clean sheets.

But Zaki destroyed him. On his return to Arsenal from Ghana, Touré's form was uncertain and he suffered another injury blocking a shot in a Champions League tie against Milan. He never hit his stride again, not helped by a bout of malaria he suffered in the summer of 2008, and after a training-ground row with William Gallas the following season, he submitted a transfer request. Although he subsequently withdrew that, he was sold to Manchester City in July 2009.

A change of scene, though, didn't make him the player of old. There were moments towards the end of last season when Touré began to look something like the player he had been in his early 20s but essentially his time in Manchester was a huge disappointment that featured two major embarrassments. He was banned for six months after failing a drugs test having taken water tablets belonging to his wife to try to control his weight and it was alleged that he had an affair with a student while hiding his identity by pretending to be a car salesman. A photograph accompanying the story that was said to show him peering sheepishly around a shower curtain only added to the impression of haplessness: even though he is said to have denied the affair, he had become a man who seemed to live in perpetual ridiculousness.

There was something horribly inevitable about his miss in the penalty shootout in the Cup of Nations final against Zambia last year (and something very characteristic about the way he volunteered to take it when Gervinho had second thoughts; the spirit was willing but the body would not comply).

At 32, the natural thought was that he was finished and when Liverpool picked him up on a free transfer this summer, the assumption was he was being brought in as reliable cover. Touré's two games so far for Liverpool, though, have suggested there may have been something concrete to those hints of a return last season. He almost scored on his debut, heading against the Stoke bar, but what endeared him to Anfield was his preposterous charge forwards quarter of an hour from time to try to support a weirdly isolated Daniel Sturridge. It was a lung-busting surge of no subtlety whatsoever, a head-down sprint that achieved nothing other than to express a desire that enthused the crowd and perhaps inspired his team-mates.

This again, perhaps, was the charismatic Touré of old: it might have been coincidence, but there seemed something significant in the fact that he was the first player to congratulate Simon Mignolet after his penalty save, and that it was he who then cleared the subsequent corner, barging Steven Gerrard out of the way to do so. This was the old Touré, taking responsibility, dragging everybody forward. Brendan Rodgers has already said Touré brings the leadership of Jamie Carragher.

That may be overstating things a little but Liverpool handled Aston Villa's potent front three better than any other side so far. Two clean sheets bode extremely well. But perhaps most important is the bond that already seems to exist between Touré and the Anfield crowd. The spoof trailer for a Being Kolo documentary shows the affection in which he is already held, even down to the joke about his "fat arse".

And perhaps that is what Touré needs. There were few expectations of him at Liverpool, far less pressure than at City. Perhaps by being accepted and appreciated for what he is rather than what he might have been, he can return to being something like the player he was, and at last move on from what Amr Zaki did to him in Kumasi.