The Blues stormed to the Premier League title last time around, finishing seven points ahead of closest challengers Tottenham Hotspur after racking up a record number of wins.
Following the penalty-shootout defeat to Arsenal at Wembley Stadium on Sunday afternoon, Cahill admitted that a quick glance at the matchday programme - which had just 20 Chelsea players listed, compared to the Gunners' 41 - highlights a potential problem.
"The back of the programme was interesting today," he told reporters. "But in terms of quality we've certainly got that and you just have to hope we don't have too many injuries.
"Obviously the new players that have just come, they're going to be vitally important for us and the quicker they settle, the better, but there's no doubt we've added quality to the team.
"They are going to be tested 100%. We'll see how that plays out, but we just have to keep everybody fit, keep everybody sharp. Rest is going to be important because we're going to have a lot of games."
Chelsea, who have Champions League football to contend with this season following a one-year hiatus, begin their title defence with a home match against Burnley on Saturday.