Ole Gunnar Solskjaer believes Manchester United's strength in depth will be crucial to their bid to win the FA Cup after they moved into the semi-finals with a 2-1 win over 10-man Norwich on Saturday.
Solskjaer's side had to work hard as Harry Maguire won it late in extra time at Carrow Road.
Odion Ighalo's opener was canceled out by Norwich's Todd Cantwell, but Canaries defender Timm Klose was sent off for hauling down Ighalo in the 89th minute.
"I'm delighted to be in the last four. Many of these players did not play the last game and now have 90 or 120 minutes in their legs," Solskjaer said.
"We made many changes...The game was not the greatest spectacle but I felt we kept the ball ok.
"It is great to have the option to rotate. Anthony Martial came on and did brilliant, but Odion Ighalo gives me a chance to rotate.
"He is a proven goalscorer and played his part in both goals."
Solskjaer made eight changes as only Maguire, Luke Shaw and Bruno Fernandes survived from the midweek Premier League win.
Both teams lacked energy and invention in the first half, as with many post-lockdown matches. In a rare threat, Maguire had to stop Lukas Rupp's shot with an alert block after Cantwell's run opened up the visitors' defense.
United finally grabbed the lead in the 51st minute, when Luke Shaw's cross was helped on by Juan Mata and Ighalo sniffed out the chance, flicking an agile finish past Tim Krul from inside the six-yard box.
Norwich nearly equalized when Ben Godfrey stretched to reach Alexander Tettey's header from Emiliano Buendia's free-kick and the Canaries drew level at 75 minutes when Cantwell's 20-yard strike swerved away from United keeper Sergio Romero.
In the final minutes, Norwich almost won it when Buendia shot just past the far post.
But Fernandes' superb flick found Ighalo on the edge of the area and Klose's panicked response, hauling down the Nigerian, triggered a red card.
With the additional extra time sub allowed, United became the first English side to make six changes in one game when Anthony Martial replaced Eric Bailly.
United dominated extra time and Marcus Rashford's strike was pushed over by Krul, who made an even better save to stop Maguire's header.
Maguire wasn't to be denied and in the 118th minute, United's pressure finally told as the England defender poked home from close range after Ighalo flicked on.