The worry Senku voices is the exact same thing Inigo is worrying about here. That they might be running out of time, that maybe he won't be able to pull them back anymore. But he knows that Tidus wants to try this, he can practically feel it radiating through his link with his friend, so he just concentrates even more, determined to focus on those two and nothing else.

Just the familiar feeling of both Tidus and Senku. Familiar, yet so far away.

One attempt, at least. Inigo's voice sounds a little tight from the concentration, but it should still be audible. The memory is a little bit more quiet now. If you guys really want to try, we should have enough time for one attempt. Count-- Count on me.

Because even though he's still tired from being pulled back himself, he'll do his darnest to let them hang in there for another moment, if it means they might be able to help Senku's world even the tiniest bit.