Tanimoto accepted the offer and has made an immediate impression on the domestic running scene, blitzing to an impressive victory in May's Christchurch Marathon with an eye-catching time of 2:24:13.
The pair also occasionally train together but 33-year-old Horspool, who finished runner-up in last year's race behind Stephen Lett, insists that should Tanimoto prevail in tomorrow's showdown, there will be no tinge of regret for his role in bringing him to Wellington.
It is great to have a quality athlete living and training in the same city, as we can work off each other. I will not be too disappointed if he beats me.
A strong elite field assembled for this year's race is further bolstered by the presence of the fastest man in the field, Adriano Bastos. The 37-year-old Brazilian boasts a lifetime best of 2:15:39, set when finishing 19th at the 2009 world championships, and although his recent form does not quite match that standard, he is pursuing a sub-2:25 time in Auckland.
With the New Zealand Marathon Championship title also on the line tomorrow, look out for three-time national 10,000m champion Aaron Pulford (Whangamata), who is set to make his debut over the marathon distance, and Jonathan Jackson (Auckland City), a podium finisher at the Rotorua Marathon earlier this year.
Leading the entries in the elite women's race is 52-year-old veteran Sally Gibbs. The Tauranga Ramblers runner stole the headlines at the 50th edition of the Rotorua Marathon last year by winning in an impressive 2:45:58 and after landing the world masters mountain running title in Wales last month, the evergreen performer is clearly in top shape.
Another interesting contender is Napier's Ruby Muir. Better known for her achievements in trail running, the 24-year-old recently switched focus to road running, winning the Wellington Marathon in July in 2:49:08.
Other lead contenders in the women's elite race will be Katie Kemp (Wellington Scottish) 2:49:55 and Kelly Parlane (North Harbour Bays) 2:52:20. Watch out also for Auckland multisport phenomenon Melanie Burke, who will be looking for a prominent showing. The 35-year-old has represented her country across several endurance sports and finished third in the elite women's race at the Kellogg's Nutri-Grain Ironman New Zealand earlier this year.