Neuville remains Rovanpera's nearest rival in the championship standings after Rally Portugal, but is already facing a 46-point deficit after the Finn scored his third consecutive victory.
The Belgian has encountered mechanical or technical issues in all four rallies to date, with his prospects of a possible victory in Portugal last weekend ending when a driveshaft failure struck during a road section.
Neuville had been sitting second overall, 7.0s adrift of then leader Elfyn Evans, but ended Friday 1m46.4s away from top spot before going on to finish the rally in fifth.
The failure triggered a boil-over of emotions from Neuville, having seen opportunities to win in Croatia and Sweden slip through his grasp following a combination of reliability issues and errors.
During a stage end interview, Neuville pointed to a picture on his phone to explain the issue before swearing in frustration.
Reflecting on yet another missed chance, he told Autosport: "Definitely [a podium was on] and maybe even a fight for the victory could have been possible.
"It would have been tough but we were right behind Elfyn before the issues, so there was a lot to play for but unfortunately the problem arrived and we did the best out of the situation.
When asked about trying to stay calm in these situations, he replied: "It is getting more and more difficult to be honest.
"It is very frustrating, we are here to fight for the championship. I have won rallies and been on the podium, but the target is to win the championship.
"We can see now that already one driver is pulling away, so there is already quite big gap and it makes it difficult to catch back up.
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"We can only congratulate Toyota on their performance and their reliability, which is something we are clearly missing. That is making a big difference at the moment.
"That is why they are so strong and that is why Kalle can score victory after victory. This is something we need very soon.
"We are close [to Toyota on performance] but we are not on the level yet, we have to work a bit more. I feel comfortable in the car and I feel I know exactly what to work on to make it faster."
Neuville's team-mate Ott Tanak has also been critical of the i20 N's reliability concerns after a challenging 2021 season during which fragility cost both he and Neuville shots at the title.
"We are quite far, there are plenty of jobs to do, and many things quite open," said Tanak.
"It has generally been difficult to get the confidence we need, but there's no other option than hard work to try and turn things around."
Hyundai has faced an uphill struggle with its 2022 Rally1 car, exacerbated by the manufacturer being the last to commit to the new rule package. The departure of team boss Andrea Adamo also affected the operation's structure, while development of the i20 N has been limited.
The car has made progress from a disastrous Monte Carlo debut in January, scoring four podiums, with its latest a third in Portugal courtesy of Dani Sordo.
Deputy team director Julien Moncet, who has been acting as team boss, is aware of the i20 N's weaknesses but says only more mileage will improve its reliability.
"We know we have a lot of work ahead of us," Moncet told Autosport.
"Sardinia is a short time [away], but we will do out best and we should really try to avoid these reliability issues. The performance of the car is okay.
"For that we need mileage and we need time. We go step by step but let's hope we will be able to fix them as soon as possible."
