Daniel Ricciardo bemoaned "the worst weekend of the year so far" as his Red Bull finished a dismal 13th in the Canadian Grand Prix.
The visibly frustrated Aussie endured a disappointing return to the scene of his first ever Formula One victory, trailing behind teammate Daniil Kvyat as he finished outside of the points in Montreal.
Ricciardo dropped four places from qualifying due to the poor performance of his Renault engine, as well as complaining of an unexplained issue with his RB11.
"I don’t mean to laugh, I really don’t. It’s either this or I cry, so I’ll choose to laugh for now. I thought the worst was past us but this weekend was by far our worse of the year," Ricciardo said to Sky Sports F1.
"I thought we had reached the lowest point but today was a new one. I don't think we really know what we need right now or where to find it."
"I was lacking pace and we are not sure why. There was nothing that felt especially wrong but we just couldn't get any pace out of the car.
"I had a few set-up changes compared to Dany but that doesn't explain the difference in pace. It is something we will look at to understand what the cause was."
Ricciardo struggled throughout the weekend, but was troubled considerably in Canada on Sunday when his fastest pace fell two seconds slower than the fastest time set by Ferrari's Kimi Raikkonen.
Asked to explain the reason behind his woes, he said: "Nothing works, we didn't have pace, it's nearly a mirror race of 2013 for me. [Then-team-mate] Jean-Eric [Vergne] was sixth, his best result of the season, and I was like 15th and we were like a second slower and didn't really have any answers for it.
"Then the year after I win and now I'm struggling to keep up with anyone on track so I don't know, I mean at the moment all I can do is laugh because race cars are complicated. Some days you don't understand them.
"Unfortunately we haven't really got on top of it all weekend but we didn't expect to be that slow in the race. That was interesting, I mean obviously I knew I wasn't fighting for points but I was still pushing and trying to get as much as I could out of it.
"It was just one of those races where you're going round and round an yeah, like, I don't know. It's like banging your head against the wall, just nothing good's coming out of it."
Ricciardo was the surprise package last season, where he finished behind only Mercedes duo Lewis Hamilton and Nico Rosberg in the drivers' standings.
But this year, an uncompetitive engine has left the Red Bull driver exasperated and whilst the likes of Honda, Ferrari and Mercedes all arrived in Canada having used their engine development tokens - Renault opted to delay their upgrades to allow work later in the season.
Red Bull's dismal performance in Canada may now force their hand, though it would cost Ricciardo a 10-place grid penalty due to the fact that they have used four engines already this season.
Asked if things could improve for Austria, Red Bull's homecoming race, the usually upbeat 25-year-old responded: "After today I think so, I hope so. Hopefully it's only up from here.
"Let’s not expect too much. Hopefully we’ve figured out the strange, cruel question mark of today by then and at least get back on the pace that I know I’m capable of."