Boss Jos Luhukay branded Atdhe Nuhiu's actions "stupid" after the striker was sent off in the closing stages of Sheffield Wednesday's defeat at Wigan Athletic.
Nuhiu, a first-half scorer in the Owls' 3-2 Championship opening-day setback, received his marching orders in the 90th minute for a second bookable offence and now faces a ban.
He had been cautioned after the break for leading with his arm in an aerial challenge and referee Tim Robinson showed him a second yellow for a similar offence as Luhukay's men chased a late equaliser.
"I must look at the video back," the manager said. "The first yellow card was correct. The second, I couldn't see what happened.
"It is stupid when he does something when he already has a yellow and has to take a second."
Nuhiu will have to sit out Wednesday's first home match of the campaign, against Hull City next Saturday.
Wednesday made a poor start to the 2018/19 season, paying the price for their defensive shortcomings against a side that finished top of League One last term
"I'm not worried, more disappointed," Luhukay said. " You expect more. We had a good feeling as a team. We want a start that we enjoyed, but this game wasn't for us.
"We had no control. And when we had the ball we would lose it. We lost every second ball, every third ball. We didn't have the quality required to play football. And then you don't have the confidence and trust.
"The opponent then feels they are stronger and can make chances and, in the end, they scored the important goals to win the three points."
The Owls were cheered on by a sold-out away following of 4,744 supporters, a section of whom booed at half-time when their side left the field 2-1 behind.
"We have fantastic support with more than 4,500 fans," Luhukay said. "But we did not enjoy this game and our fans cannot be happy with this game and result."