The newly-appointed director of football was only able to bring in QPR striker Loic Remy on a season-long loan deal, but he maintains it was not for a lack of trying.
Writing in his programme notes ahead of the Premier League game with Hull City, he said: "It was very frustrating that we did not add at least another signing to the squad in the recent window, but it was not for lack of effort.
"It was not an easy task to improve the quality of the current squad with the financial resources at our disposal, particularly in a window in which the value of players was grossly over-inflated and the demands of agents likewise.
"I worked very hard on several targets and we made a number of bids for players, but for various reasons - some of which were outside the club's control - we were unable to secure our targets.
"We will continue to operate in a financially responsible manner, buying only the right players for the right prices and not paying over the odds or making costly knee-jerk decisions.
"This is the reality of a well-run football club that lives within its means. When the deal is right and the player can add real quality and depth to the squad, we have the ability to spend."