Ronaldo was involved for the full duration on Saturday as United were held 0-0 by Watford at Old Trafford.
Manchester United interim boss Ralf Rangnick has emphasised “we have to play with the players we have available” and that he started Cristiano Ronaldo against Watford after the forward declared himself fully fit.
Having played 85 minutes of the 4-2 win at Leeds last Sunday and then all of the 1-1 draw at Atletico Madrid three days later, Ronaldo was again involved for the full duration on Saturday as United were held 0-0 by Watford at Old Trafford.
The contest saw the 37-year-old have an effort ruled out for offside and fail to convert a number of other opportunities.
While Ronaldo has scored 15 goals for United this term, his strike against Brighton on February 15 is the only one he has netted since the turn of the year.
Rangnick was asked after the Watford match if he had concerns over the amount Ronaldo was playing and it was put to him that it looked to be taking its toll on the Portugal international.
The German said: “Yes, but we have to play with those players we have available.
“I spoke with him (on Friday) before the game, before the training session. He told me he was fully fit to play and that’s why I decided to have him in the starting XI.”
Edinson Cavani has not been involved for United’s last five matches due to injury, and Rangnick said: “Edinson is not available and we don’t have that many other central strikers.
“I brought on in the last 15 or 20 minutes Marcus (Rashford) plus Jadon (Sancho), so almost all the offensive players we have in our squad were on the pitch.”