Manchester City cruised into the last 16 of the FA Cup with a 4-0 win over Championship side Fulham at the Etihad Stadium on Sunday.
Pep Guardiola's side became the first team in the top five European leagues to reach 100 goals in all competitions this season.
"For a few moments I thought it would be a tough game," Guardiola said. "They're a team with a lot of courage but it was a bit different after the red card."
City were awarded a penalty after six minutes when Ream brought down Jesus in the penalty area. Ream was sent off and Gundogan scored from the spot.
The hosts scored a second after 20 minutes when Silva curled the ball into the bottom corner from outside of the area.
Guardiola's side are well placed to reach the League Cup final as they hold a 3-1 lead heading into the second leg of the semifinal against local rivals Manchester United on Wednesday.
However, a tougher test awaits in the Champions League, where City meet Spanish giants Real Madrid in the round of 16 next month.
"The determination was always there and we will fight to win each competition," Guardiola added. "Next is United and a chance to get to the final and that is our next target."