Shefki Kuqi scored six minutes into his Oldham Athletic debut but they were held by rivals Huddersfield Town.
The deadline day signing headed home from six yards after a fine run and cross by Bradley Diallo.
The Terriers levelled when Antony Kay volleyed home via the post from 12 yards out from Gary Roberts' corner.
Oldham played the last 15 minutes with 10 men when Diallo was sent off for a reckless challenge on Oscar Gobern, and Town's Alan Lee hit the bar late on.
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Oldham manager Paul Dickov told BBC Radio Manchester:
"Last thing I said to them was show me the desire I know you've got and don't come in the changing room leaving anything out there, and I think they did that.
"The big man (Shefki Kuqi) will score goals, he's had two training sessions and goes out and puts in a performance like that.
"I thought he (Tom Adeyemi) was fantastic, he's got an old head on young shoulders and to be a top midfielder he's got all the ingredients."
Huddersfield Town manager Lee Clark told BBC Radio Leeds:
"I'm a little bit disappointed because I feel we missed three or four gilt-edged chances to have taken the three points.
"I'm not disappointed with the performance, I'm very happy with that because Oldham started unbelievably well. We were under the cosh for 10 minutes, they scored a good goal.
"The lads have stuck together well and responded well, got the equaliser and then for the next 25 minutes of the first half we were creating the opportunities.
"We've had some unbelievable chances in the second half, Gary Roberts, Lee Novak, Donal McDermott all missed more than half-chances. We're a little bit frustrated, but not downbeat."