Ziyech opened the scoring against Villarreal but was substituted before halftime after suffering a shoulder injury in a collision with Juan Foyth.
Chelsea went on to win 6-5 on penalties after Gerard Moreno’s second half equaliser took the game beyond extra-time.
Ziyech could now be set for a spell on the sidelines as Chelsea await the results of a scan for the 28-year-old Moroccan international.
"If you take a player out during the first half it's serious," Tuchel told BT Sport after the game.
"We overused some players who were absolutely not ready to play 120 minutes and have only two days in between this and the next match with Crystal Palace so that absolutely does not help us.
"We came (to Belfast) with so many players who did not even play a friendly match so far so this is the situation - we have to adapt and we have to, in our mindset, be as ready as we can be to do our very best."
Ziyech joined Chelsea from Ajax Amsterdam last summer and made 39 appearances across all competitions, scoring six goals as the Blues won the UEFA Champions League.
