Jhon Duran grabbed Villa's winner as Saints failed to muster a shot on target over the game.
Afterwards, Martin said: "It's another mistake and not a shot on target is madness really, for how many times we stole the ball in the first half.
"We just give teams a lead too many times and for such poor goals. At some point, when a team scores a good goal or a bit of individual quality you can accept it.
"The goal was just so poor. We kick it long to two of the smallest players on the pitch when we don't need to because we have a scary moment just before it.
"It comes back and then we press well, force it to one side of the pitch and we two against one with the striker and somehow he ends up with the ball and scores.
"It's madness and it's like those lines that just hurt us too many times really, just so many times and the goals we have conceded this season are so poor."
He added on the stat of zero shots on target: "I don't know. We had one where Flynn Downes was in the middle of the goal, Cam Archer in the box.
"I don't know what more I can give the players to make them really believe that extra spark because when you're bottom of the league and it's been tough games...
"Some really quality opposition, tough results, difficult decisions with VAR, difficult injuries, suspensions, a season's worth almost a quarter of a season.
"It's been interesting, to say the least, and difficult to deal with so I don't know what, other than stop the game and tell the players how good they are.
"You want to tell them at that point what they can go and do to give them that little bit of spark and belief in the final third because we stole the ball a lot."