"We're pleased with the result but not with the performance," said Gatland who was named as forwards coach for the Lions tour of South Africa by Ian McGeechan and Gerald Davies last month.
"We only had 19 turnovers against South Africa last Saturday but we had 30 tonight.
"We didn't respect the ball enough and tried to force our passes. Our skill level let us down. We need to go over the tape and be analytical as we prepare for next weekend.
"We're not happy but we have to put this behind us. There were some positives, we scrummaged well and it was great to see Leigh Halfpenny get a couple of tries and he looked dangerous."
Wales were given a fitness scare when fly-half James Hook limped off in the 18th minute with a tendon injury to his right knee.
The Ospreys star had hoped to secure the No10 jersey ahead of rival Stephen Jones for next weekend's clash with New Zealand but he is now a doubt for the clash at the Millennium Stadium.
"James got a knock on his knee and needs a scan," added Gatland.
"We will know more in the next 24 hours but we're hopeful he will be fit for next week."
Canada left the Welsh capital in upbeat mood after they followed up their hammering by Ireland with a much-improved display.
"I think we've put the pride back in the Canada jersey," said Cannucks coach Kieran Crowley, whose side face Scotland next Saturday.
"I was really pleased and impressed with the heart showed and I thought our defence was outstanding.
"We didn't over-commit to the tackle area and did really well. The guys deserve a beer and a few days off before we face Scotland."