Chelsea manager,Thomas Tuchel says his team did not show enough “courage” in their close 1-0 win over Barnsley.
The Blues reached the FA Cup quarter-finals thanks to a winning goal from Tammy Abraham.
The Englishman scored in the 64th minute after being assisted by substitute Reece James.
Abraham was also the hero of the other side. He headed a Barnsley shot over the line after Kepa Arrizabalaga failed to clear the area.
Chelsea will now play Sheff Utd at home in March to try to secure their place in the semi-finals.
Speaking after the match, Tuchel told BBC Sport: “We switched to a back four and took Marcos [Alonso] out for this tactical change. Andreas [Christensen] had to leave because his head hurt. The changes made it a bit easier to get into the opponents’ half and overcome the first pressure.
“We did well at the beginning of the second half and constantly played in the opponent’s half.
“We scored the goal and I had the feeling that they increased the risk but we stepped down in the small decisions. We didn’t have enough courage and he was too deep for a long, long time.
“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.”