Ross County manager Derek Adams expects his players to cope better with crossed balls after conceding four headed goals in the defeat by Celtic in Dingwall.
Virgil van Dijk and Joe Ledley scored a brace apiece in the Glasgow club's first league win against the Highland side.
"Defensively, we haven't done well enough," said Adams.
"The cross ball into the box is something we need to improve on. It's been the story of our season."
County substitute Ivan Sproule fired in on the rebound in the 68th minute to claw back the deficit to 2-1, but it was scant consolation for Adams' side as Ledley headed in twice in the space of five minutes to seal a comfortable win for the visitors.
Adams insists his side were playing well until van Dijk's opener as half-time approached, but felt poor concentration cost his side dearly.
"We've been working on it, but individually, we have to do better," said Adams.
"The game plan was to try and limit Celtic to opportunities in the first half, and we certainly did that successfully.
"Celtic had good possession, but Mark Brown didn't really have a save to make, then we gave a goal away from bad defending and they were 1-0 up at half-time.
"We were quite happy for them to have the ball - it was important to stay in the game at that point.
"It was a huge disappointment. To get ourselves to 2-1 and then lose a goal to make it 3-1 quite quickly after that."
Adams added that while the defeat was a blow to his players, he would regroup for the replay against St Mirren after last week's encounter was adandoned due to rain with County 2-0 down.
"We've played Celtic twice in our first 11 games. It's not the games against Celtic we'll be judged on, it's the games against other teams.
"St Mirren have yet to play them, so from my point of view we have to look at it and go to St Mirren and try to take something from the match."