Borthwick-Jackson put in another excellent display at Stamford Bridge, with his cross leading to Jesse Lingard’s opening goal.
However, the 19-year-old played Diego Costa onside when the Chelsea striker scored a late equaliser. Van Gaal praised Borthwick-Jackson despite the mistake.
“We continued with our good, attacking football,” van Gaal said.
“We have created a lot of chances here at Chelsea. It’s a nasty away game, I think, and one that’s not so easy. The last few years Manchester United haven’t won here so it’s not an easy match – and we took the lead with a fantastic goal. A fantastic cross also. Then you can control the game, but in the last quarter we gave it away.
“There are many details which are responsible for that. We had a lot of free-kicks around the penalty area against us and we survived. Chelsea have very good set-plays and they have scored a lot from set-plays, so we were well organised. But then we have a goal like that – Daley Blind slipping and Borthwick-Jackson not taking the line of the defence. Costa is not offside because of that.
“It was such a pity because Borthwick-Jackson was playing fantastically and I was very proud of him. It was a superb performance until the last quarter. It’s sad for the fans also. This match you heard only the Manchester United fans and not the Chelsea fans.”
Borthwick-Jackson has enjoyed a rapid progression into the first team at United but he has not looked out of place despite his tender years.
The goal conceded against Chelsea will be a lesson for him but the fact remains that he has been superb since being thrown in at the deep end at Old Trafford. He will likely keep his place in the team for the trip to Sunderland next weekend.