Ellis could not hide his disappointment after a third home defeat of the season left Tigers in fourth place in the league table with four games remaining.
But he said the players would work hard to recover in time for the last two months of the season.
“It just shows that a week can be a long time in rugby,” Ellis said. “From last week when most things we tried went right, this time most things went wrong. The difference between our performance at the Millennium Stadium and then this week is unbelievable.
“We dropped off tackles, we did not play smart enough, we let them play too much and, credit to Wasps, they deserved to win. They were clinical and finished their chances well.”
Tigers do not have a fixture next weekend, but will use the time to build up towards the EDF Energy Cup Final and the remaining Guinness Premiership fixtures against Bristol and Harlequins at home, and away to Bath and Newcastle Falcons.
“We have a lot of things to work on,” said Ellis. “We had a confident feeling after last week but you cannot just pull on the jersey, you have to fight for it.
“The players will hold up their hands and say it was not good enough. But we will regroup and do some hard work on the training pitch and in analysing what we did wrong and try to put things right.”
