Grant Hall has told Queens Park Rangers’ official website that their recent poor run of results was playing on the squad’s minds.
Rangers beat the Millers 3-0, and Hall says that the reason Hasselbaink’s start was so slow at Loftus Road is because the players were just getting used to his methods.
“We’re pleased for everyone, especially the gaffer," Hall said.
“The Championship is such a tough league and going into a new job is always difficult, especially in this division.
“He’s come in and made changes to get his points of view across in terms of how he wants the team to play, so there’s always going to be a transitional period.
“It was eight games and that starts to play on your mind a bit, especially when we feel we’ve actually done okay in most of the games."
The inauspicious start Hasselbaink has made has seen concerns rise at Loftus Road, but his side's recent victory gives him a foundation to build upon.
QPR’s chances of making the play offs already look very slim, meaning that the pressure could reduce - with expectations becoming lower around the London club.
The R’s are currently in 15th place in the Championship table, and they are 11 points back from the top six.
QPR’s next match comes against Wolverhampton Wanderers on Saturday, before they face Nottingham Forest.