Many times we, as coaches, are approached by eager parents who would like us to fine-tune their kids' games immediately before the tournament ("hey, ________ has a match on Saturday so is it OK if you could give him a good hit on Friday").
My personal theory is that matches are won or lost well in advance of the tournament (CHAMPIONS ARE CREATED ON THE BACK-COURT NOT CENTER COURT). It's how you approach your practices 2-3 months prior to the tournament that has a greater bearing on your results. Sometimes, a "good" practice can in fact be counterproductive because the player is overloaded with new information that s/he has not been able to process, synthesize, implement and refine. Consequently, there is a chance that the player enters the tournament with too many thoughts in his/her mind. This is the fallacy of fine-tuning in that it's difficult to fine-tune something that hasn't been "tuned" in the first place. Second, a great deal of players have the tendency to play better in a tournament when their immediately preceding practices have not been the "best". These players use these bad practices as ways to motivate themselves for the match. In other words, they don't take their Saturday morning match for granted because they know how easy it is to be thrown off their game by the opponent. Such players go out there and actually concentrate better during the match and compete hard for every point.
As a result, it is more important for players to set up their practices in such a way that they peak for the main event. An effective process would be to have consistency/stamina-focused practices well in advance of the tournament (T[ournament]-minus 2-3 months) and the add more power and precision-based practices as the player gets closer to the main tournament. Smaller tournaments during this period should be used as testing grounds for what the player practices. For example, if the player is working on his backhand, he should try to play some tournaments where he focuses on working his backhand around the court. Maybe go for no winners with his forehand and try to get as much practice hitting backhands as possible.
Then, as the player gets closer to the main tournament, practices should alternate between consistency, power and precision so that the player is comfortable executing the same on a day-in day-out basis. The last few weeks before the tournament (T minus 2-3 weeks), every practice should contain a consistency, power and precision component. Only after mastering the foundation and fundamentals can the player be assured that some last-minute fine-tuning will have any effect. However, the good results come from the player's knowledge that she's given it her best during the foundational practice stages.