Chelsea fell to just their second league defeat under the German however with the Blues boss admitting he had made a mistake in making so many changes to his regular starting XI.
And Merson has warned the Londoners could struggle to rediscover their rhythm on the big stage.
Tuchel made too many changes in that game. He said so himself. And it backfired. I thought it was extraordinary.
You’ve come this far. Play your best team. The name of the game was to get a top four spot sewn up before the final.
‘Instead, he made loads of changes, they lost, and the door is now open again for the teams who are chasing them down.’
Chelsea have also booked a place in the Champions League final against Manchester City with Merson wary more changes during the final games of the season could leave them with nothing.
He continued: ‘I know you have to try and keep people fresh and it’s been a long season but in a big game like that you have to play your best team.
‘Chelsea could end up with two trophies and a top four finish this season. Or they could end up with nothing.
It’s all on a knife-edge, and they’ve put themselves under pressure.’