Saturday's 1-1 home draw with relegated Bury was a sixth draw in the last seven matches for the Saddlers - and a third on the spin.
But Smith was angry with two decisions by officials which he felt cost his team victory, although they extended their unbeaten league run to 15 games.
"Bury's equaliser was offside and the goal James Chambers scored for us and was disallowed was not offside," Smith insisted. "And one of their players should have been sent off."
However, Smith admitted his team did not reach their usual standard, adding: "It was our worst performance for a while.
"We were poor on the ball and we have had problems with the pitch. We couldn't get enough water on it and it was always going to be a case of who dealt with the misplaced passes.
"It was a long shot for us to reach the play-offs but I feel angry and frustrated that we have not won today, no matter what happened with results elsewhere.
"But we have done well this season and just fallen short at the end."
Febian Brandy scored his seventh goal of the season in the 21st minute to give Walsall the lead but cash-strapped Bury salvaged a point in the 90th minute when one of their only two substitutes, Efe Sodje, tapped in after Jonson Clarke-Harris hit the crossbar with a free kick.