"The event is pretty open and having done so well last time I was in the States, at the US Open, I feel I've got a good understanding of how to play in those conditions.
"If I can execute my gameplan well enough I feel I can be dangerous irrespective of who I'm up against. Having qualified, there's relatively little pressure on me so I can hopefully use that to my advantage."
The British No1 added: "I felt quite tired during the recent European indoor events and physically I wasn't feeling that great so I didn't enjoy the tournaments as much as I would have liked to.
"Having been in a good position in the Champions Race for much of the year I felt under quite a bit of pressure to qualify, so it was very satisfying to do so."
Carlos Moya of Spain and Argentina's Gaston Gaudio complete the Red Group alongside Federer and Hewitt.
Controversially, the event organisers have chosen to play it outdoors, even though the players have spent the autumn contesting indoor tournaments in Europe.
Marat Safin has been highly critical of that aspect, but Henman sees no cause for concern, particularly after his achievements at Flushing Meadows in September.
Meanwhile, Russia's Svetlana Kuznetsova beat her fellow countrywoman Vera Zvonareva 6-2, 6-4 in the opening match of the season-ending WTA Tour Championships in Los Angeles.
In the other group, former world No1 Serena Williams defeated Russia's Anastasia Myskina 4-6, 6-3, 6-4.
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