Penalties provided Simon Mignolet with a shot at redemption in the Capital One Cup final but like his attempts to deny Jesús Navas, Sergio Agüero and Yaya Touré in the shootout, he could not quite get there. Wembley witnessed the good and bad of the Liverpool goalkeeper in microcosm and he will look back with bitter regret at the error that contributed to his club’s misery and left Jürgen Klopp with a major decision to make on his goalkeeper come the season’s end.

Manchester City were worthy winners despite requiring the vagaries of a penalty shootout to claim the trophy but they were indebted to Mignolet for their only goal against a Liverpool defence that comprised Lucas Leiva and Kolo Touré for 95 minutes. Klopp arrived at Wembley seeking the win that would strengthen belief in his reign but exited with further evidence of the faultlines that have undermined too many Liverpool performances. They existed at both ends of the pitch in the club’s 12th League Cup final appearance.

Klopp has been steadfast in his support for the Belgium international but the goalkeeper’s entire Liverpool career was encapsulated by one inconsistent afternoon at Wembley. Smart and sharp when turning Agüero’s first-half shot on to his left-hand post, weak and lax when Fernandinho’s angled drive somehow flew through his guard at the near post to open the scoring. Mignolet’s unreliability will have come as no surprise to those Liverpool fans who issued a collective groan when the Wembley screens replayed a shot that, though hit with brute force by the Brazilian, did not change its trajectory en route to the net despite a 6ft 4in goalkeeper standing in the way.

The immediate reaction is to consider the mistake that decided a cup final as the moment Klopp’s faith in his No1 changed. Perhaps it will, and those persistent stories of a Liverpool move for Barcelona’s Marc-André ter Stegen or Stoke City’s Jack Butland will come to fruition in the summer, but that would be to overlook Klopp’s influence on the award of a new five-year contract to Mignolet only last month. The manager was instrumental in securing the services of the “smartest keeper I have ever worked with” for the long term and has backed the 27-year-old at every available opportunity. But vulnerability at crucial moments demands a rethink from the manager come the end of the season.

Mignolet, ironically, was instrumental in taking the final to extra time once Philippe Coutinho had equalised from one of Liverpool’s few efforts on Willy Caballero’s goal. Having foiled Agüero impressively in the first half, the keeper denied Fernando and Yaya Touré at close range in the final moments of normal time. He bettered those stops with a crucial reflex save from Agüero in extra time after the Argentina international had been slipped through on goal and looked certain to score until Mignolet intervened. It was also, of course, his saves in the penalty shootout against Stoke City in the semi-final that helped book Liverpool’s return to Wembley in the first place. His blend of important stops and lapses presents a genuine dilemma for Klopp.

A performance that took an age to ignite raised the prospect Liverpool strengthening in several departments this summer, although the never-say-die commitment of the players was faultless and essential to their late, dramatic improvement. So too was Klopp’s willingness to take risks when trailing, bolstering his attack with Adam Lallana and Divock Origi in the final stages as James Milner ended the contest as a makeshift left-back.

The service to Daniel Sturridge from midfield was particularly limited with Jordan Henderson and Emre Can often too deep with their defensive duties to assist their leading striker. Sturridge was on the periphery throughout with his best work arriving as a creative rather than clinical force, engineering good chances for Milner and Coutinho in normal time that neither could take.

In contrast to Agüero, who shimmered with menace, Sturridge was relatively subdued on what was his chance to repay Liverpool for their perseverance during his many absences through injury. The striker had spoken forcefully in midweek about the feeling of devastation his various fitness problems have caused and scorned suggestions his issues are as much of the mind as body. “To say a player doesn’t want to play is the biggest disrespect ever to any footballer and it’s astonishing,” he said. There was no disguising his emotions after the final whistle as he climbed the Wembley steps with tears rolling down his cheeks.

The City fans did not greet Sturridge’s every touch with the same level of venom that Liverpool’s reserved for Raheem Sterling but it was noticeable. Like Sterling, he left his cup final opponents under a cloud having rejected City’s offer of a £75,000-a-week contract in 2009 – after making three league appearances that season – to join Chelsea as a free agent.

City received only a £3.5m development fee for their young player of the year, albeit with add-ons and a 15% sell-on clause taking the eventual sum to £7.3m, and relatively small change for such a big talent.

They would take more compensation from the fit-again Vincent Kompany’s domination of their former striker in the final. The wait for a first trophy at Liverpool for Sturridge, Mignolet and others goes on.