Thomas Tuchel claims Chelsea lacked 'courage' and 'rhythm' during their 1-0 win over Barnsley in the FA Cup fifth-round.
Chelsea have progressed to the quarter-finals of the competition after Abraham tapped home the decisive goal from inside the six-yard box following a low ball across the box from Reece James.
However, the Blues manager was left feeling 'frustrated' by their performance and claims he 'expected more' from his players against Barnsley - who are currently 13th in the Championship.
Speaking after the game, Tuchel told the BBC: 'We changed to a back four [at half-time] and took Marcos [Alonso] out for this tactical change. Andreas [Christensen] had to go out because he had a headache.
'The changes made it a little easier to get into the opponents half and overcome the first press.
'We did it well at the start of the second half and played constantly in the opponents half.
'We scored the goal and I had the feeling that they increased the risk but we stepped down in the little decisions. Not enough courage and it was too deep for a long, long time.
'We clearly can play better, so yes I expected more but not in terms that I am frustrated.
'If you lack a rhythm and a bit of self-confidence and you have to show on this pitch, against an opponent that takes all the risk and plays the game of his life, that is not easy. We can do better but I don't want to be too hard on the players.'
Chelsea will take on Premier League strugglers Sheffield United in the quarter final of the competition.
The two sides will go head-to-head at Chelsea's home ground, Stamford Bridge, on the weekend of March 20.
Tuchel believes it will be a 'tough' encounter, but says he is happy to be playing the fixture on their home turf.
'It's going to be a tough one. They are a very physical team that presses high,' he said. 'They are organised but I am happy to have a home game. This is what we wanted.'