Oldham boss Lee Johnson was disappointed his side failed to build on their opening-day win after losing 1-0 to Walsall.
James Baxendale's 25th-minute goal proved the difference as he fired home from 10 yards after Oldham's defence had failed to clear an Adam Chambers cross.
Johnson, meanwhile, was convinced Latics were denied two blatant penalties, one for a handball and another for a foul on Korey Smith.
"The effort was not bad and we had a go in the second half, but things didn't fall for us. We lacked energy and fizz," he said.
"I recently went on a managers course and we were shown all kinds of handballs. "That was a stonewall and a banker. I mentioned it to the referee (Gary Sutton) afterwards and he told me that maybe it was a penalty.
"It is not an easy job. You get some decisions, but we didn't get that one."
After Latics lost 1-0 in the cup against Derby in midweek, Johnson was also worried after seeing his side fire a blank for a second successive game having hit four goals in the league at Stevenage in last Saturday's impressive 4-3 success.
"People say we have goals in us, but that was not the case here. We weren't potent and that is a bit of a worry," he said.