THE board had just gone up showing four minutes of added time as Daniel Sturridge fed James Milner in the penalty area, writes JOEL RABINOWITZ. His first touch was heavy, just keeping the ball in play as he floated the ball to the back post, where Dejan Lovren, leaping like a salmon, towered above Adrian Ramos to slam a header into the back of the net at the Kop end to send Anfield into delirium.

Liverpool 4 Borussia Dortmund 3. The Reds are into the Europa League semi-finals after an iconic European night at Anfield that will go down in Liverpool folklore. Just 13 minutes before Lovren scored the winner, his defensive partner Mamadou Sakho had given Liverpool hope with a header of his own from Philippe Coutinho’s corner.

Two of the most unlikely heroes, given that neither player had scored all season until that point, before sending Thomas Tuchel’s side back to the Westfalenstadion in a state of shock and despair. The two legs could not have been more contrasting, with Sakho and Lovren the embodiment of Liverpool’s performance throughout the tie.

In Germany, they were imperious at the back, nullifying Dortmund’s attacking threat with an outstanding defensive display of courage and discipline. At Anfield, Liverpool were torn apart inside 10 minutes by Dortmund’s ruthless counter-attacking play. Sakho, in particular, was at fault with his poor positioning. Marco Reus added a third away goal on 57 minutes, which looked like a killer blow at the time.

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Then Philippe Coutinho scores his ubiquitous long range belter. Sakho then equalises and Lovren wins it at the death. From despair to ecstasy in 90 minutes. Sakho and Lovren embraced each other after the full-time whistle. They made their mistakes but they came out on top in the end against a very, very good side.

The results have been mixed during Jürgen Klopp’s first six months on Merseyside, but this was evidence of what Liverpool are capable of now and, more importantly, what they could be capable of in the future.

The shape, organisation and discipline of this side are vastly improved since Klopp first arrived. Sakho and Lovren have emerged as Klopp’s first-choice centre back pairing, and what was very recently a real weak spot in the team has become an area of relative strength.

Lovren in particular has enjoyed a highly impressive season having revived his Liverpool career from the brink after a torrid first season at the club. Klopp has instilled a new-found sense of confidence as Lovren appears transformed from the erratic, error-prone defender of last season.

The 26-year-old Croatian now plays with a clarity of thought that deserted him last season, cutting the mistakes from his game and executing the simple things well. He no longer overcomplicates his role in the team. Lovren knows exactly what Klopp wants from him and he now looks closer to the £20million player who signed from Southampton and had Jamie Carragher and Gary Neville purring about his ability on Sky Sports.

Lovren deserved that special moment against Dortmund more than anyone. It takes a strong character to come back from last season and he deserves great credit for turning it around.

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His partner, however, continues to split opinion like no other. Sakho has become very much a fan’s favourite at Liverpool — his likeable personality and sheer passion for the club endearing him to the supporters.

Yet the performances of the France international, a £16million deadline day signing from Paris Saint-Germain in September 2013, have a tendency to oscillate between the extremes.

Sakho’s showings in the away legs against Manchester United and Borussia Dortmund in the Europa League were truly outstanding, yet his first-halves against Tottenham and Dortmund at Anfield were borderline calamitous.

Sakho was named PSG captain aged 17 and has regularly been a first choice pick for France. He is clearly a very talented defender but his unorthodox style creates an impression that he is on the brink of a error. He isn’t most of the time. He likes to play out from the back — something Klopp encourages from his defenders. His passing is sometimes excellent but often high risk.

It’s all part of the package with Sakho. He’s a powerful presence in the air and he reads the game well, often in the right position to lurch out with one of his gangly legs to make a vital block or interception. He does have a mistake in him — as is so often stated — but so does every defender. And it’s a position in the team where those mistakes are highlighted more than most.

Barney Ronay recently described Sakho as a “drunk Baresi” in reference to the legendary Italian defender, which more or less sums him up perfectly. Joey Barton, meanwhile, suggested that: “Watching him is similar to viewing a clown spin plates. You are just waiting for them to smash on the floor. Yet somehow, he keeps it going.”

For a man whose opinion is often worth casting aside, Barton was spot on here.

There is a tendency among fans to view players in binary terms, but football doesn’t work like that. Neither Sakho or Lovren are truly world-class defenders; players that will have agents knocking from the world’s elite. They never will be. But they’re not average or poor either.

Perhaps we should just accept that both are very good, with the capacity to have the odd poor performance. They also have a burning desire to succeed at this club, which goes a long way. We saw that against Dortmund. They simply refused to let their side go out. And their work as a partnership is something to be encouraged by.

The dilemma facing Klopp then revolves around the arrival of Joel Matip, 24, from Schalke, who will join the club on a free transfer in the summer. Described by goalkeeper Ralf Fahrmann as one of the best defenders in Germany, Matip is very highly thought of in the Bundesliga. You would expect him to come to Liverpool with a starting place in mind, not to sit on the bench.

Klopp therefore must decide whether to break up the settled partnership of Sakho and Lovren to accommodate Matip, who possesses many qualities Klopp looks for in defenders — pace, height, strong reading of the game and composure in possession.

At this point, a Matip-Lovren partnership looks the most likely scenario, although Klopp may gradually ease Matip into English football to begin with.

If, as looks to be the case, Lovren would be first choice to partner Matip, it is quite possible that Sakho would not want to accept a squad player role. Aged 26, he retains a strong reputation in Europe and would have a significant market value (£13.5m if you want to take the Transfermarkt website as read). In this scenario, if Sakho did want to move on, summer could be the right time to cash in on his services.

Regarding the other options at Klopp’s disposal, Martin Skrtel looks to be heading for the exit in the summer and rightly so. The 31-year-old Slovakian has always been an erratic, inconsistent defender during his eight years at the club and this summer is surely the right time for him to move on. His calamitous second-half performance in the 3-2 capitulation against Southampton was the final straw. Skrtel has no future under Klopp.

Kolo Toure, on the other hand, has never let the side down when called upon this season. Toure’s deal expires at the end of the season, but there is a strong case to offer a one-year extension to the 35-year-old veteran. Toure is a hugely popular figure at the club and would offer vast experience for the likes of Joe Gomez to learn from and look up to. It would be a shame to see him leave as he would be happy to accept a bit-part role and fill in when necessary.

Speaking of Joe Gomez, he showed enough in the early stages of the season, albeit at full back, to suggest he will be an important player for Liverpool in years to come.

Somewhere down the line he has the potential to become a first choice option at centre back, but next season will come too early for that as he will only just be returning from an ACL injury. Gomez is an exciting talent and certainly one for the future who Klopp will be glad to have in his squad next season.

There is of course the forgotten figure of Tiago Ilori, but the 23-year-old is very much on the periphery and looks a long way off the senior squad.

Whether he’ll make it at Liverpool is highly doubtful, but it could be worth sending him out on loan to a Premier League club (not Aston Villa) to see what he’s about. Alternatively, Deportivo La Coruna have been linked with a move for him, and a permanent deal would probably suit all parties.

When it comes to building a solid defence, team shape and organisation are arguably more important than the individual players.

Leicester City are on course to win the Premier League with Wes Morgan and Robert Huth as their first-choice centre back pairing. Neither are top drawer defenders, but they have thrived in the right set up.

Klopp may of course look to add another new face in the summer, but there are other areas of the squad in far greater need of further investment. Extending Toure’s deal could save some funds for elsewhere.

Sakho and Lovren have proved their ability to perform on the big stage against high calibre opponents this season, and while Matip is less of a known quantity, his reputation from Germany suggests he has the tools to succeed under Klopp.

It remains to be seen who will be the first-choice pairing next season, but competition for places is healthy. It is worth noting that all of these options, aside from Skrtel and Toure, are aged 26 or younger, so there is time for Klopp to develop them as players and refine their skills.

In Lovren, Matip, Sakho and Gomez, Klopp has four very capable defenders to choose from who are more than good enough to form the backbone of Liverpool’s side next season.

@_lfcjoel