Aside from Dumoulin himself, Haga and Laurens ten Dam are the only two riders from the 2017 Giro d'Italia Team Sunweb line-up to return with the Dutchman's squad, in for the 2018 corsa rosa.
Last year, Team Sunweb put up a spirited defence of Dumoulin's jersey, but he was visibly isolated in the third week in the mountains, particularly after the loss of Wilco Kelderman because of a crash in the second week.
This year, like all squads, Team Sunweb has been reduced by one rider, from nine to eight, for the Grand Tours. Last year fast-man Phil Bauhaus was part of the Giro d'Italia line-up, but Haga tells Cyclingnews, the team have scrapped any secondary objectives completely in favour of a purely GC-focussed team.
"As a squad, it's really climber-heavy, this time there's no sprinter," Haga said early in the race.
"I'm considered a little bit of a climber and I had that role last year, but this time around I'll be one of the guys dropped earlier on the lower slopes of the mountain stages after doing my work. He'll have support from other riders" - like Louis Vervake and Sam Oomen - "higher up the climb.
"We've definitely beefed up on the mountains, so on those stages I'll be able to use my energy more on the lower parts of the climbs to support Tom until the race really kicks off. It's a really well-rounded team for a GC bid."
As for Haga's own condition as the Giro gets underway, he says, "I'm definitely better than two years ago, and I'm aiming to be better than last year. Hopefully, I'll be able to go the distance.
"I've given the route a cursory look and it's a typically tough Giro route, some big days, some big mountains, and some big days in really big mountains. They always say 'one day at a time', but the three days in Sicily are going to be a tough challenge."
Although temperatures eased in Israel on Sunday, Haga said the previous heat wave made "for a really brutal kickoff."
Looking further ahead for himself, the Texan says he aims to "have a crack at the Nationals'. Normally I don't get a chance to do that, and then I'd love to race the Worlds. But that's a way down the road."