Saturday's one-day multisport race in the Bay of Plenty is the latest in a series that has pitted the rising Allan against Ussher.
Ussher dominates the world multisport scene and has won at least 38 international races in the last five years.
The younger athlete has been snapping at his heels this year, leaving also-rans and multisport commentators to wonder when and where Allan will "get Ussher".
Allan finished second to Ussher in this year's Coast to Coast and at the inaugural 3D Multisport Championships in Rotorua.
They raced against each other again, in teams, at the Wulong Mountain Quest, in China last month, where Ussher's team won and Allan's team was third.
Both athletes are strong cyclists and in January, Allan went 14min faster than Ussher in the Challenge Wanaka 180km team cycle, which is ridden as a time trial - although it was a few minutes short of the cycle course record set by Ussher in 2010.
Allan's friend and training partner Gavin Mason predicted a big race between Allan and Ussher this weekend, but said the ultimate goal was to prepare for next year's Coast to Coast.
The Motu Challenge was being treated as an indication of where they shaped up nationally, early in the season, Mason said.
Joining Allan and Mason in Opotiki are veteran athletes Andrew McLeod of Wanaka and Shaun Portegys of Alexandra, Allan's cousin Dan Moore, of Nelson, and "JJ" Wilson of Christchurch.
While Allan would be chasing Ussher, the supporting southern contingent would be just "trying to hang on", Mason said.
Veteran Opotiki multisporter and sports writer Jim Robinson said this week many of the sport's followers believed Ussher might not race next year's premier multisport event, the Coast to Coast, in February, following an announcement he had entered the individual Challenge Wanaka long distance triathlon in January.
Because the showdown might not occur next year, there was more interest in other races Ussher and Allan were entering throughout the season, Robinson said.
"Actually, I do [pick Allan to win] but it is going to be so close.
It could come down to the run into town. The river is very high now. When the river was low, which was two days ago, it would have suited Richard because he's such a strong paddler. But now it is high and I don't think Richard will get away from Dougal easily," Robinson said.
Former Coast to Coast and Motu Challenge champion Gordon Walker is not competing this weekend but rapidly improving Opotiki athlete Sam Clark (21) is in the field and is expected to do well.
Clark has the 2009 two-day Coast to Coast title under his belt and has the advantage of racing on home ground.
Elina Ussher (wife of Richard) is the favourite in the women's Motu Challenge field but could face a strong challenge from Louise Marks of Auckland, Rachel Cashin of Taumarunui, and Sia Svendeson of Christchurch.
The Motu Challenge comprises a 65km mountain bike, 17km run, 52km road bike, 27km kayak, 8km road cycle and 3km run, and has attracted 260 entries.
Another 101 athletes have entered the event's sister-race, Motu 160, which combines the long mountain bike and road cycle stages.
