The Wales international rolled his ankle in the opening tour game against New Zealand Provincial Barbarians and has essentially been left playing catch up ever since, earning some further minutes in the 32-10 win over the Maori All Blacks on Saturday.
Warburton has conceded that he could be left out against the world champions next week and, after overlooking him from the Lions' 23 for the midweek meeting against Chiefs in Hamilton, Gatland admits that he has some tough calls to make.
"There's no doubt that there's some pressure on certain players and certain combinations have gone well," he told reporters. "A lot of those guys who played against the Crusaders did exceptionally well and, last night's performance against the Maori, we dominated territory and possession and we squeezed the life out them, an unbelievably talented backline that just went nowhere.
"For Sam, look, we were hoping he was going to be part of the 23 against the Crusaders. Unfortunately, he rolled his ankle a little bit so hadn't recovered in time. So he had time against the Highlanders and we were able to give him time last night. There will be some tough debates and discussions to have on the final make-up of what the back-row is going to be for Saturday."
The Lions have now won three and lost two of their tour outings, with just the Chiefs left to face before their showdown against New Zealand.