Chelsea lost striker Alvaro Morata to a knee injury as they drew with MOL Vidi in a Europa League dead rubber.
The Blues, who had already won Group L to reach the last 32, made 10 changes although Willian, Morata and Cesc Fabregas were among the starters.
Willian opened the scoring with a free-kick before Chelsea teenager Ethan Ampadu headed into his own net.
Loic Nego put Vidi ahead with a fantastic volley but Olivier Giroud scored a stunning free-kick equaliser.
Morata hurt his knee while shooting from Callum Hudson-Odoi’s cross late in the first half and had to be replaced by Giroud – who is now the Blues’ only fit striker.
Boss Maurizio Sarri says he does not think the injury is too serious, with an update expected on Friday.
The Blues had won their opening five Europa League games, and are joined in the knockout stages by Bate Borisov, who beat PAOK Salonika in the other game. Vidi could have qualified – but needed to better the Belarusian side’s result.
Chelsea short on striking options
Did Sarri need to name such a strong team for an ultimately irrelevant match in Budapest?
He even admitted before the game that it was a “difficult match to prepare for” with nothing on the line.
They named two players under 21 in their starting line-up, with another two on the bench. Arsenal named twice as many for their match in similar circumstances against Qarabag.
Chelsea only have two established strikers at the club – excluding those out on loan – and they could be down to one depending on the severity of Morata’s injury
Eden Hazard – who was rested for this game – started up front in Sunday’s 2-0 win over Manchester City and might be needed to reprise that role again.
Sunday’s Premier League trip to Brighton is the first of seven games in three weeks.
Blues’ fringe players fail to impress
Chelsea’s two teenagers had mixed fortunes with usually impressive defender Ampadu, already a senior Wales international, heading past his own goalkeeper from a flicked-on corner.
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Forward Hudson-Odoi had another bright game and forced two saves from Vidi’s Adam Kovacsik.
Morata – who has only managed 10 goals in 2018 – looked short on confidence again, missing several chances before his injury.
And players like Emerson Palmieri, Ross Barkley, Ruben Loftus-Cheek and Fabregas did little to stake a place in the first-choice line-up.
Willian, the only player to keep his place from the win over City, opened the scoring with a central free-kick, which Kovacsik should have stopped.
Only 116 seconds later Vidi were level from Ampadu’s own goal.
The hosts then led when Nego, a former Charlton Athletic player, hit a brilliant volley past Willy Caballero from Georgi Milanov’s cross. He had already forced two saves from Chelsea’s back-up goalkeeper by that stage.
But substitute Giroud saved their Europa League unbeaten record with a fine free-kick that not even a defender on the post could keep out.
‘Satisfied with the character’ – quotes
Chelsea boss Sarri: “We made a lot of mistakes from the tactical point of view. I am very happy with the character and with the reaction from the second goal.
“On the pitch there was a lot of young players so it wasn’t easy to react.
“From the tactical point of view we made a lot of mistakes. We lost a lot of ball. We can manage the ball better I think. At the end, especially with the young players I am satisfied with the character.”
