The 20-year-old is set to deputise for John Ruddy, who must serve a one-match ban after his sending off at Chelsea before the international break.
Diss-born Rudd only has a handful of appearances to his name, including the 4-0 Carling Cup defeat to MK Dons, while his first job at Stamford Bridge was to pick Frank Lampard's penalty out of the net.
However, the Canaries boss has complete faith that England Under-21 squad man Rudd will be up to the challenge as the Norfolk club look for a first top-flight victory in front of the live TV cameras against the winless Baggies.
"I have got no fear about Declan playing - no fear," Lambert told a news conference.
"He has never let himself or me down, so I haven't got any problem [with him playing]."
Lambert decided against recalling Jed Steer from his loan spell at Yeovil or bringing in an experienced stopper ahead of transfer deadline, so 17-year-old Academy keeper Remi Matthews looks set for a place on the bench.
Summer signing James Vaughan could be in line for a belated debut, the striker having been hampered by a knee problem since his arrival from Everton.
Centre-half Zak Whitbread is a doubt with a hamstring problem picked up at Chelsea, but otherwise Lambert expects a clean bill of health from Norwich's returning internationals.
Steve Morison impressed for Wales against both Montenegro, scoring in the 2-1 win and then England at Wembley, where midfielder Andrew Crofts also featured.
Lambert said: "I don't think Morison lacks confidence anyway - and I thought Crofty was excellent, I really did."
Roy Hodgson's men have lost all three of their league games so far, but two have been against Manchester United and Chelsea before they went down 1-0 at home versus Stoke to a last-gasp goal.
Lambert, though, is not expecting anything other than a stern examination from the Baggies.
"I went and watched them against Stoke and they played really well - and I thought they were excellent against Chelsea," Lambert said.
"They could have been two-up before Chelsea scored and I think they are a really solid side - really good.
"It will be a really tough game for us."