Richie Porte's face finally settled into a wry smile on the final climb of stage 17 of the Giro d'Italia, a clear indication of how much the Australian was willing to dig deep to help Ineos Grenadiers leader Richard Kalapas win the Maria Rosa in the final Grand Tour. It was a clear indication of how deep he was willing to dig.

"That's my role," Porte said matter-of-factly after receiving comments from the assembled media about how hard he had worked as the last man standing for Calapaz on the stage to Lavarone.

"We all believe in Richard and we know he is a great leader, so it's easy for us to give our all for him. He's very calm, he's more professional than anyone else on the bike, and he probably wants this more than anyone else. So it's great to have him and it's great for morale within the team.

There are four stages left in the Giro d'Italia. If all goes according to plan for Ineos Grenadiers, it will be four days of defending Maria Rosa in a battle that is often measured in minutes at these stages, but now counts in seconds.

The last time Calapaz won the Giro in 2019, he was 1:54 behind his closest rival, Vincenzo Nibali, at the end of stage 17. This time, there are four riders within that time, first Jai Hindley (Bora-Hansgrohe) by just 3 seconds, then Mikel Landa (Bahrain Victorious) by 1:05 and Joao Almeida (UAE Team Emirates) by 1:54.

"I've never seen everyone so close in a Grand Tour in the final week," Porte said.

"It's good from a TV point of view, but we still have a lot of hard days ahead of us. Tomorrow is a bit of a relief for me, but who knows what will happen on a stage like tomorrow."

Thursday looks like a sprinter stage with a flat 156km from Borgo Valsgana to Treviso, but then comes two mountain stages, and at the end of stage 20, a tough 14km climb of the Passo Fedaia before the Verona Time Trial is waiting in the wings.

While Saturday's summit finish at Passo Fedaia (via Passo Pordoi, the race's highest point) casts a big shadow, there is no sense that the overall contenders will wait until then. For starters, Friday's stage 19 (178km) includes a winding Kolovrat climb with a 5km section of 10.4% gradient.

"It's definitely a super hard climb and technical downhill, but you never know what's going to happen in the Giro, even tomorrow," Porte said, from his 2010 Grand Tour debut to a three-day maglia rosa, an untimely puncture, a controversial time penalty, and a 2015 race-ending crash in 2015.