Bruno Fernandes scored a hat-trick and Paul Pogba created four goals, both operating at times in the area holding midfielder Phillips usually patrols.
But after a pre-season drastically shortened by his starring role in an England team which reached the final of the European Championship, Bielsa put Phillips on his nine-man bench and did not bring him off it. Robin Koch was instead asked to hold the midfield.
"Phillips is a player who always shines," said Bielsa when asked how significant his absence was in the defeat. "I don't think it's a question of individuals as to why we couldn't play a more balanced game.
"It was very difficult for us to recover the ball and it was very difficult for us to create any danger.
"It was for a number of reasons, none of them the high press or the individual performance
of a player."
Of German international Koch, a centre-back by preference but not unused to playing a defensive midfield role, Bielsa said: "I liked how he played. I thought he was a dynamic player, he was present, he was willing, committed. He made lots of effort and he had presence throughout the game."
Fernandes played in the hole for the Red Devils, but cleverly made Koch's life more difficult by moving into so many different positions. Often when he did, Pogba drifted in off his nominal left-wing position to good effect.
Leeds also lost by a four-goal margin on their previous trip to Old Trafford, beaten 6-2 in December. Bielsa did not want to draw too many comparisons.
"In the previous game there were moments with a big difference between the two teams, in this game those moments were less," he argued.
In December Leeds caved in right at the start of the game and could not pull it back. In this case it was the start of the second half.
Fernandes gave the hosts a 31st-minute lead which Luke Ayling cancelled out but Bradford-born Mason Greenwood responded two minutes later with the first of four goals in 16 minutes, a run completed by a Fred tap-in.
Junior Firpo made his debut for Leeds as a second-half substitute.