With six riders grouped inside 90 seconds at the top of the standings going into Sunday’s final time trial, the 100th Giro d’Italia is set to provide what could be the tightest ever finish to one of the three great Tours. The Colombian Nairo Quintana wears the pink leader’s jersey after the last mountain stage, but breathing down his neck are three men: the defending champion, Vincenzo Nibali, France’s Thibaut Pinot and the Dutchman Tom Dumoulin.

Respectively, the trio are 39, 43 and 53 seconds behind Quintana, and two others have an outside chance – of the podium if not the final win – the Russian Ilnur Zakarin and the Italian Domenico Pozzovivo, who are 1min 15sec and 1min 30sec back. On the flat 29.3km from the Monza race track to Milan’s Duomo, Dumoulin – a dominant time triallist thus far and in last year’s Tour de France – looks to hold the aces but the race is too close to call; after three weeks in the saddle the riders’ states of fatigue will decide the outcome.

Quintana’s manager, Eusebio Unzue, believes the lanky Dumoulin will become the first Dutch winner of the Giro and Pinot appears to think the same – “it’s made for Dumoulin” – but the Dutchman was rightly circumspect. “I had a good day, but the time gaps tomorrow won’t be as big as in the previous time trial, definitely not,” he said. “I will have to fight for every second.”

Nairo Quintana takes pink jersey off Tom Dumoulin after dramatic stage 19 Read more

Saturday’s final mountain stage to Asiago was a relative stalemate over the toughest ascent of the day, the 24km climb to the war memorial atop Monte Grappa, with the closing hostilities reserved for the short ascent to the plateau where the finish was located. There, Pinot looked the strongest, eventually taking the stage win after making his escape along with Quintana, Nibali, Pozzovivo and Zakarin.

Dumoulin rode the perfect race however, remaining within touch if not in actual contact, along with a second group of five riders; he eventually lost 15 seconds, although Pinot received a 10 second bonus for his stage win that could prove vital.

The gold standard for suspense in a three-week Tour remains Greg LeMond’s eight-second victory on the final stage of the 1989 Tour de France, and this could well provide something similar. That was a see-sawing two-way fight with Laurent Fignon, this is a subtly different four-way contest, but this is a scenario the organisers could barely have dreamed of after a torpid first week’s racing when the favourites observed each other closely.

The race took shape after the time trial stage in Umbria when Dumoulin gained so much time on the climbers that it became obvious they would have to carve out a substantial advantage going into Sunday’s time trial.

He backed that up with a hilltop stage win last Saturday, opening a gap of almost three minutes. That meant the final week’s racing in the Dolomites has centred on the attempts by Quintana, Pinot and Nibali to dislodge him and gain time, along with Dumoulin’s corresponding efforts to remain in close enough touch for his time trial strength to tell in full. He may just about have managed that.

That scenario has made for an enthralling contest, typified by Friday’s stage when Dumoulin made the basic error of being caught at the back of the group on a descent early on and Nibali, Quintana, Pinot and Zakarin took flight with a host of their team-mates in support. That led to 50km of intense battle, four squads riding flat out at the front of one group, four others – led by Dumoulin’s Sunweb men and Adam Yates’s Orica – chasing full bore at the head of a second string less than a minute behind.

As well as suspense, the final week has been marked by a Giro staple: what the Italians term polemica – a war of words between the race leaders, avidly inflated by the press. The discussion has centred on bodily functions and professional ethics, prompted by an episode on the toughest mountain stage of the race – two ascents to the snowdrifts of the Stelvio on Tuesday – when Nibali and Quintana pressed on after Dumoulin was forced to make a toilet stop late on, pulling into the roadside and stripping to his shorts, to the consternation of television commentators.

After their attack, Dumoulin called the Colombian and the Italian out for what he viewed as underhand conduct, although television images appeared to show Quintana and Nibali waiting initially as the race leader chased, fruitlessly. The following morning he and Nibali – whose verdict on the Dutchman was particularly harsh – were made to shake hands for the television cameras, although neither man appeared at ease.

Given that tense background, there was immediate speculation on Friday that Nibali and Quintana had escaped while Dumoulin had dropped to the back of the group to urinate on the move. The Dutchman quashed that rumour later, but that summed up the mood of intrigue. Sunday should prove to be a cliff-hanger, but at least in a mere 30km there should be no need for anyone to take a toilet break of any kind.

Stage 20 results

1. Thibaut Pinot (France / FDJ) 4:57:58” 2. Ilnur Zakarin (Russia / Katusha) ST 3. Vincenzo Nibali (Italy / Bahrain) 4. Domenico Pozzovivo (Italy / AG2R) 5. Nairo Quintana (Colombia / Movistar) 6. Bob Jungels (Luxembourg / Quick-Step) +15” 7. Adam Yates (Britain / Orica) 8. Sebastien Reichenbach (Switzerland / FDJ) 9. Bauke Mollema (Netherlands / Trek) 10. Tom Dumoulin (Netherlands / Sunweb)

Overall classification

1. Nairo Quintana (Colombia / Movistar) 90:00:38” 2. Vincenzo Nibali (Italy / Bahrain) +39” 3. Thibaut Pinot (France / FDJ) +43” 4. Tom Dumoulin (Netherlands / Sunweb) +53” 5. Ilnur Zakarin (Russia / Katusha) +1:15” 6. Domenico Pozzovivo (Italy / AG2R) +1:30” 7. Bauke Mollema (Netherlands / Trek) +3:03” 8. Adam Yates (Britain / Orica) +6:50” 9. Bob Jungels (Luxembourg / Quick-Step) +7:18” 10. Davide Formolo (Italy / Cannondale) +12:55”