Richards is joined among the replacements by Danie Coetzee who is available after a leg injury.
"The Tigers will provide another real test for us," said Smith whose team recorded an important home win over Worcester Warriors last weekend.
"We got our Premiership season back on track last Sunday. The players held their nerve in very difficult conditions against a rapidly-improving Worcester team.
"We will be asking the players for another big performance against a team that are as formidable as any we are likely to meet in this country or in Europe."
London Irish team (v Leicester Tigers, Welford Road, Saturday 2.45pm)
15 Delon Armitage
14 Topsy Ojo
13 Gonzalo Tiesi
12 Seilala Mapusua
11 Sailosi Tagicakibau
10 Shane Geraghty
9 Paul Hodgson
1 Clarke Dermody
2 David Paice
3 Richard Skuse
4 Nick Kennedy
5 Bob Casey (c)
6 Declan Danaher
7 Steffon Armitage
8 Phil Murphy
Replacements
16 Tonga Lea'aetoa
17 Danie Coetzee
18 James Hudson
19 Juan Leguizamon
20 Richard Thorpe
21 Peter Richards
22 Eoghan Hickey
