With his Friday running having been limited by an intercooler problem and then an issue with his pedals, things did not improve much on Saturday.
He faced fresh car problems in final practice and then struggled to find a good pace in qualifying, eventually ending up 10th on the grid after his final laptime was deleted for running wide at Copse.
After facing the brunt of Ferrari's issues, Vettel was clear that he did not think the team was paying any less attention to him than Charles Leclerc, who will start fourth, and that he could only see things getting better.
"I don't want to accuse anyone of bad intentions," he told C4. "From my side it was not ideal today.
"I had a lot of trouble finding the rhythm. As I said, I am relatively confident that tomorrow will be better. How much I don't know. I can't promise anything, but it can't get much worse..
Asked about what had gone wrong in qualifying, Vettel said: "The honest answer is I don't know. I mean, I struggled a little bit to get into the groove and into the rhythm, which around here is important.
"Yesterday, we didn't get much running, not many quality laps, and this morning, we had another small issue. So yeah, not ideal, but equally, I thought the car was okay.
"I struggled to put it together. So I think it's probably more me just making sure everything comes together. So not a good good session, but let's see what we can do tomorrow."
He later added to Sky: "Tomorrow we'll be on the wrong tyres at the end of the queue, at the end of the top 10, so it won't be a piece of cake."
Vettel has confessed, however, that the situation of him knowing his time at Ferrari is coming to and end is not making life especially easy.
"[It's] not ideal," he said. "I mean, not an easy year so far. Obviously now the races come very quick. So that can be a pain but can also be a blessing.
"Obviously the last two days haven't been good and therefore we lost a little bit of momentum. I thought that other than that, the first weekend was trouble, the second weekend didn't really happen. The third weekend was sort of the first smooth weekend and now we're in trouble again. So it's been a bit of a rough start, but you know, there's not much choice.
"I'm determined to hang in there. I think the guys are pushing as much as they can. I don't think there's any bad intentions by anyone. So we obviously had some issues yesterday and this morning, but we have to, I guess, at this stage pull through and we'll come out on the other side."
Additional reporting by Lewis Duncan and Norman Fischer