An own goal from Lewis Miley, along with strikes from Jayden Bogle, Dominic Calvert-Lewin and Noah Okafor, condemned Newcastle to a heavy loss at Elland Road on Monday night, with Bazoumana Touré's goal proving nothing more than a consolation.
It was the first defeat of the season for Jaissle's young side, who had gone unbeaten in their opening five matches across all competitions before being outplayed in West Yorkshire.
The result left Newcastle United in the bottom half of the Premier League table after four matches, having gone into the game knowing victory would have lifted them as high as third. Thiaw, captaining the side for the fifth time this season, fronted up to reporters afterwards to address a performance he admitted fell well short of the standards Newcastle expect of themselves.
"A lot of emotions, a lot of things going through your mind," Thiaw told reporters in the mixed zone at Elland Road. "Obviously one is the disappointment. You take it personal. I am really, really, really, really disappointed tonight.
"You can just say sorry to the fans. How we performed, the result... it's not what Newcastle want to be."
Asked whether a heavy defeat was somewhat inevitable for a young Newcastle squad across the course of a long season, the Germany international rejected the suggestion the club's inexperience could be used to excuse the performance.
"I wouldn't take this as an excuse because I think that's the team we have," Thiaw said. "It's going to be this team this season so I don't take this as an excuse. We still have quality. Overall, what's more important than quality is attitude, the energy we have to bring. Leeds were just better than us today in these kind of terms."
Jaissle's side will look to respond quickly, though the manner of the defeat, and Thiaw's blunt assessment of it, suggests the head coach will want a marked reaction from his players in the matches to come as Newcastle look to arrest their slide down the early-season table.