Mark Warburton said he felt he had to take Luke Amos off against Barnsley because QPR needed more pace in attack.
On-loan Tottenham midfielder Amos was replaced at half-time by winger Olamide Shodipo.
The change saw Dominic Ball sit in midfield with Ebere Eze and Ilias Chair playing behind Jordan Hugill up front, with Shodipo and Bright Osayi-Samuel on the flanks.
Rangers improved in the second half but still struggled to create clear-cut chances.
“We wanted to get more pace up top,” manager Warburton explained.
“Mide has trained very well and we wanted that pace.
“It was purely tactical, with Dom sitting in there with Ebere and Ilias behind Jordan.
“I think you saw we moved the ball quicker in the second half and we looked much better.”
Warburton’s side went six matches unbeaten before the season was suspended because of the coronavirus outbreak.
That run took them to within six points of the play-off places.
But they made a dismal return to action and the 1-0 home defeat all but ended their faint hopes of a late challenge for promotion.
Hugill missed two second-half chances, while Eze went close with a second-half strike.
“As a team we let ourselves down,” Warburton admitted.
“We had to manage the game better. It was really poor for the first 45 minutes. We were 1-0 down and it could have been two.
“In the second half we were much better but still probably only six out of 10. Still no shots on goal.
“Then we created chances and you have to take those chances - even when you’re playing below your best you’ve got to take your chances.
“We weren’t troubled in the second half and we moved the ball quicker. But then at that point you have to take your chances and we didn’t do that.”