The Pole suffered damage to three tyres on the first four stages of the event and, with only one spare Michelin aboard, he was unable to make the journey to Lisbon for the superspecial stage. Kubica was running second in WRC 2 when he retired.
When he was forced to retire with a lack of useable tyres on the road to Lisbon, only rising Finnish star and factory Skoda driver Esapekka Lappi was ahead of him in WRC2.
"I am surprised, I drove very good stages for me today," he said. "I cannot say I am happy, there is still a long way to go and I have to work a lot for sure in the future.
Ogier leads from Sordo in Portugal
"But to be here, for the first time on gravel and to be able to drive like I did in three stages, it was a good piece of work from my side."
He added, however, that the Portuguese roads had posed more of a challenge than he had expected.
"It was a mixed day today," he said. "In the first stage I struggled for grip and had very poor confidence, but that improved in the second stage, where we had one small moment when we slid off the road over a crest.
"It is very difficult to drive here for the first time and additionally for me with no experience [of gravel rallying]. These are very, very difficult stages with a lot of crests. I was a bit surprised on some corners.
"For me, it is difficult to judge when you drive [in the recce] at 50kph, how a single crest will affect the car.
"You cannot say: 'OK, I back off on these two corners and I will only lose two seconds,' because it is practically every three corners that there is a crest of a jump or something affecting the car."
Talking about his retirement from the event, he said: "We cut the rear tyre and [another] rear tyre was slightly off the rim. The tyre lost the air slowly and we had no chance to arrive [in Lisbon] with only one spare."
As well as his tyre issues, Kubica had been forced to repair the radiator after the second stage, when a branch went through the front of his car.
He will return under Rally 2 regulations tomorrow.
At the sharp end of things, Sebastien Ogier extended his lead over Dani Sordo to 4.4 seconds after finishing second-fastest on the superspecial that closed Friday's Rally Portugal running.
The Volkswagen driver found two seconds on his Citroen rival over the 3.27 kilometre Lisboa stage.
Sordo had earlier closed by more than eight seconds over SS3 and SS4, with Ogier admitting his decision to select soft tyres all round was "not perfect."
Ogier also complained of a "small problem" which had tempered his approach to the superspecial.
Sordo's Citroen stablemate Mikko Hirvonen won the stage, finishing 0.9s ahead of Ogier.
In doing so he closed to within 4.8s of Jari-Matti Latvala, who was third on Friday's final stage.
Thierry Neuville drifted away from the podium fight in fifth, 30s down, but he enjoys a comfortable gap to a chasing pack led by M-Sport team-mates Evgeny Novikov and Nasser Al-Attiyah.
Martin Prokop meanwhile jumped ahead of the Mini of Michal Kosciuszko and into eighth.
Kosciuszko had to contend with a loose bonnet after dislodging it over a jump early on in the superspecial.
Ogier charges clear in Portugal
Ailing Ogier fears for Portugal fitness