"It was a really tough leg for us. We're not very happy to finish fifth in the leg at all," he said.
"It all played out pretty fast really. We left Newport and all was going pretty well at the start but it all happened quickly.
"The guys carried on riding at the front and we fell out. We jibed north, did worse than the other guys and got stuck in a high-pressure bubble. The other guys kept riding out front for a couple of days and we were screwed.
"It's a shame. We were pretty fired up to extend our lead but that's racing. It is what it is. It's been a real test of character in the last week. Now we have a fight on our hands."
The result leaves MAPFRE one point behind Dongfeng, who continue to be a pillar of consistency in the race, and two ahead of the surging Brunel.
The fifth-placed finish means MAPFRE need a strong finish in the remaining two legs, though their series form suggests the latest effort will be merely a blip on the radar.
Tuke said the stage was set for a thrilling finish to the race as they try to overcome both Dongfeng and Brunel.
"I think both pose big threats. Dongfeng have sailed a pretty consistent race right from the outset and have been the quickest boat," he said.
"Brunel are definitely the form boat and nearly won three in a row. We've got Pistol Pete and Brunel right up there with Brunel and it's going to be a great battle.
"That's what racing is all about. If you don't enjoy those close battles then you shouldn't be doing it. We're going to try to step up and sail a couple of good legs."
MAPFRE started rough in the Newport to Cardiff leg as they never really found their groove. They ended up more than four hours behind winners Brunel.
There has been some criticism of the focus MAPFRE have put on leaders Dongfeng and while Tuke said there had been times they had kept a close eye on them they've altered their view.
"There's certainly been legs in this race where we've concentrated on them too much," he said.
"Some of those legs turned out all right. We were third into Auckland when we were criticised for covering them too much.
"Since then we've been sailing our own race and in this case we probably had the same tactics and tried to lead the group to the north.
"I like it when we're close to them but we didn't see another boat the whole leg last time. We were in the fog within 20 minutes."
An underlying narrative during the race has been the battle between Tuke and Burling for sailing's first triple crown.
The triple crown is the combination of an Olympic gold medal, America's Cup victory and a Volvo Ocean Race title. Both Tuke and Burling teamed together on the first two but are now in tight contention to complete the trio.
While they may be great friends on land, Tuke was under no illusion about who was going to be the first to wear the crown.
"We're [MAPFRE] going to get it [triple crown] first," he said.
"We're still very confident here. We obviously have some things to work on and this is definitely a setback, but we're confident that we'll win."
The penultimate leg from Cardiff to Gothenburg, Sweden, begins on June 10.
