Coventry City Manager Russell Slade said that the red card shown to skipper Jordan Willis was pivotal in the 3-0 defeat at Northampton.
Slade told the Press Association: "We started the game well and I thought we were the better side. But the sending-off was pivotal, it gave Northampton a huge lift and put us own to 10 men which was always going to be difficult.
"I've had a look at it and I think it's a bit harsh because he's won the ball but caught their player with a trailing leg.
"We managed to get to half-time without conceding but the first goal was always going to be key. And it was the team with 11 men who got it but you can't throw the towel in even when things do go against you.
"Going 1-0 down seemed to sap the players and you can't allow that to happen, you have to be big enough and strong enough to respond in those situations. We had no real response when Northampton got the second goal so it was a very difficult afternoon for us.
"But the goals we conceded were nothing to do with us being down to 10 men, so there are no excuses for any of them."