Saracens arrive in Reading just one point adrift of the title play-off zone, having won four from their last six league matches, while they are also firmly on course for a European Challenge Cup quarter-final place.
Saracens also boast the Premiership top points-scorer this term in fly-half Glen Jackson, with centre Andy Farrell and flanker Richard Hill also beginning to make their presence felt following prolonged injury battles.
Smith said: "We will be facing an in-form Saracens. Alan Gaffney has worked his magic on a talented squad of players.
"Wherever you look, there is real class from full-back through the backs to the tight five and back-row.
"We are expecting as tough a game as any we have played all season, and know we will have to be at our best to secure any points."
Smith will make a late decision on 20-year-old Shane Geraghty, who was named in England's Six Nations squad earlier this week.