Sunday’s 2-1 defeat at Aston Villa means Chelsea head to Porto having lost three of their last four matches.
Those losses include being beaten by Leicester in the FA Cup final.
“Yes, it concerns me – because it always concerns me when we lose,” Blues boss Tuchel said at a press conference on Monday.
But the German insisted Chelsea have been unlucky and that their overall performances have been good.
He explained: “It’s not so easy to get a grip on these losses, to analyse them, because the data and statistics we produce, and the performances we produce, do not indicate that it’s logic to lose.
“But still, it’s a fact that we lost. So we are concerned because it’s the worst feeling for me to lose.
“It’s a bit too much (to say) that we are unlucky in the last weeks. I don’t like to stress it too much because it seems like we talk about it too many times.
“But it is like this. We were simply not lucky in these games. We cannot deny that we had good performances.
“So, yes and no; we are concerned but there is no second thoughts – there is only all in for Saturday’s match.”