Gatland's forwards were dominant but the Lions backs were outplayed by the Blues, the worst performing of New Zealand's five Super Rugby teams this season.
Fielding a completely different 15, Gatland's men conceded the contest's opening try within six minutes when Rieko Ioane surged past Jack Nowell.
"It felt like there were lots of positives about today, some of our set piece stuff was good".
But a brilliant late try from Ihaia West secured victory for the Auckland side, the replacement fly-half latched onto Sonny Bill Williams's superb offload to scorch under the posts from halfway.
"The medics think he'll be fine during the week and should be OK", said Gatland. So we definitely need to tighten up in that area and be hard on ourselves.
True to form, the Lions used their brawn to get back in the hunt via Stander, before the bruising Williams scored a lucky try on the half-time hooter.
Batman star Adam West dead at 88
He is survived by his wife, Marcelle, as well as his six children, his five grandchildren, and two great-grandchildren. Adam West , one of the most iconic actors to ever wear the Batman cape and cowl, died on Friday at the age of 88.
It proved to be a hard test against the Super Rugby side, with the hosts taking the lead through a Rieko Ioane try on seven minutes.
"We have improved from the opening game with the time we have spent together and we will improve again before Saturday".
"We've been concentrated on ourselves and we haven't anxious about too much externally".
CJ Stander touched down to level the scores and Leigh Halfpenny made no mistake with the conversion to put the Lions ahead.
The start wasn't auspicious, as the Blues settled the quicker and took the lead through an unconverted try from the hugely impressive Ioane, but the Lions were quick to force their way back into the game.
West kicked the Blues further ahead after the interval before the Lions rallied, despite losing Liam Williams to the sin bin, two Halfpenny penalties giving them a slender lead.
11 players will earn their first cap for the British and Irish Lions when they play the Blues.
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