Ricciardo set a time that would have been good enough for 10th place in Q1, but it was quickly deleted for a track limits offence after he went wide and off the track at the top of Eau Rouge.
The AlphaTauri driver admitted that the mistake was costly and stressed that he would have been faster had he not gone offline.
"I think as well I lost a bit of time from the track limits," he said when asked by Autosport about the frustration of his deleted laptime.
"Basically I tried to take Eau Rouge full, like I entered full and I felt the car start to move. And so I had a little lift, and it just then put me a bit offline and then I was kind of on the wetter part of the track, and I couldn't really do much more.
"I kind of just had to let the car go. I tried to save it. Yeah, frustrating obviously.
"On one hand this is what quali is. My intentions were good to try and take it full, I thought it could have been done, but obviously a little error then put us out."
Ricciardo admitted that he was looking forward to having a second chance to show his one-lap pace in the shootout session that decides the sprint grid.
"Right now how I feel I'm very happy that I get another chance tomorrow," he said. "That's kind of numbed a little bit of the pain.
"And yeah, I think it's back to the laptops and get into the data. I think we'll probably have similar conditions tomorrow, so see how that puts us.
"Obviously the result today is frustrating, disappointing and all of that. But I think Q1 I was there, the first run I was a little bit further away, and then I think that lap without the Eau Rouge thing, I probably could have picked up a little bit more time.
"I think we're there within a couple of tenths also and excited to go in Q2 and obviously see if I can keep chipping away.
"So I think generally the speed is there, and that's important, there wasn't too much head scratching, I think there's still obviously things we can improve, but it was positive it's just obviously a shame to start Sunday now at the back."
Ricciardo conceded that it wasn't ideal to have his second event with AlphaTauri be a sprint weekend with a compressed timetable, with the Spa rain adding extra spice.
"It's a challenge, but it just kind of forces us to get on with it," he said. "A conventional weekend is better because we can try a lot more with the set-up and I can feel the car and the limits more, what does the front wing do, what does this do.
"But I like kind of just getting in and going for it, and I think that's why with limited running I felt fairly content with the pace that I was showing.
"Obviously there's still a bit more to find, but I felt in Q2 I could have kept finding those extra few tenths."
