Oldham 0-1 Walsall
Walsall maintained their strong start to the season as James Baxendale's first-half strike made it three straight wins for the Saddlers.
Oldham thought they should have been awarded a penalty when Cristian Montano's shot appeared to strike a hand but the referee disagreed.
The hosts paid the price for failing to clear Adam Chambers' cross, allowing Baxendale to score from 10 yards.
Latics defender James Tarkowski saw two goalbound efforts blocked.
VIEW FROM THE DRESSING ROOM
Oldham Athletic manager Lee Johnson told BBC Radio Manchester:
"We were poor in the first half and better in the second half. We had the majority of the ball in the second half but it didn't quite fall for us.
"It's three games in a week, and it's been an intense week, and it took us to take a punch on the nose before we could start coming back.
"It wasn't all bad - there were some good bits in there - but just not enough of them."