The Saddlers created several opportunities in the first half to take the lead but were reluctant to shoot, meaning many of the chances were wasted.
Mat Sadler was sent off at the beginning of the second half for a deliberate handball and Oldham took full advantage, strolling to a 2-0 victory.
And Clarke said he is urging his strikers to take shots on goal after they left him frustrated with the scoring drought up front.
“Mat (Sadler) was very apologetic in the changing room," he said.
“He’s an experienced player, he knows he’s let the boys down. It’s an obvious one.
“It’s an angry changing room, all the staff are very angry, one or two of the players are angry.
“There’s some weak minded players at the minute that need to get themselves into gear. Mentally weak, weak minded.
“We ride the first 10, 15 minutes, ride a few set pieces, never looked in any danger.
“We controlled a lot of the first half but we don’t take shots.
“Why don’t you take shots, players not taking responsibility.
“Work good movements, good angles and it’s frustrating for the supporters, it’s frustrating for me and my staff.
“We don’t teach them to walk the ball in.
“If you don’t take the opportunity then the ball breaks down and it’s frustrating.
“That’s weak minded.
“Josh (Gordon) has a shot, he nearly clears the stand, but take the shot.
“It’s been on three, four times in the first half to take the lead.
“I had a chat about that at half time and then second half Mat gets sent off for a silly decision and he knows it.
“Stuart Sinclair for example, he gives absolutely everything on there.
“The heart, the desire.
“Don’t get me wrong, not everybody can be a Stuart Sinclair that works so hard, keeps the ball, keeps it ticking along.
“Runs 20 yard sprints to stop a blatant goal.
“Other players can show desire in different ways.
“Taking shots, taking responsibility, final product.
“That’s the frustration for me, they’re not doing it.
“We don’t work balls for strikers to get into one on ones and then pass it, we work to finish."