With 12 players on World Cup duty, the makeshift Tigers line-up was exposed by Saracens during a crucial period just before and after half-time.
"There's no getting away with it, you've got to make your tackles. It hurts you," said Cockerill, of the slack defending which allowed Ernst Joubert, Owen Farrell and Jamie George to cross for tries in that devastating 20-minute spell.
Those scores turned a 16-6 deficit into a 35-11 margin and killed the match.
"The second try they scored and the ones just after half-time; you've got to make your tackles. If you don't then you get punished and they get away from you."
Cockerill is looking for good news from the World Cup soon, with some players returning as their nations are eliminated from the tournament and the England management due to make a decision on Thomas Waldrom's immediate future.
"I'll be asking them to make a decision in the morning on whether he's going to be flying back tomorrow or not," added Cockerill.
"We go to Bath next week and then we have Harlequins here, and then we might get the odd one back."
Saracens director of rugby Mark McCall was understandably pleased with his team's performance, which inflicted Leicester's worst ever Premiership defeat.
He said: "I think our fundamentals were really strong today; and the line-out was outstanding. Then we just got a bit of momentum in attack."
He was also delighted to continue the enviable away record which helped Saracens to reach last season's final, adding: "If you look at our away record last year it was very good. We won nine of our Premiership games away from home, so we don't pick and choose when we get up for games. The players try to get up for every game."
But he conceded that his side's three consecutive wins at Welford Road showed the ground did bring out something special in the players.
"This kind of ground and this kind of stadium excites the players. A big part of that is the crowd and the players enjoy that," he said.
"We had a lot of younger players on the field today - Jamie George, Will Fraser, Jackson Wray, Ben Spencer, Owen Farrell, James Short - and it's great experience for them, and I thought they did really well."
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