The abdominal region is very important for most sports. The comprising muscles of the core (front and back) allow flexion, extension, and rotation to occur. What we sometimes forget is that these muscles also control anti-flexion, anti-extension, and anti-rotation. A variety of crunches and back hypers have their place, but don’t forget about training to be able to resist and absorb sagital, frontal, and rotational forces as well.
Multi-joint weighted barbell and dumbell exercises are typically great exercises and have an added benefit of training balance and stabilization of the core muscles.
Various static holds and planks are good training tools to be able to maintain posture and resist outside forces.
And don’t get too hung up on whether or not you have a six-pack. Washboard abs are mainly a reflection of low body fat percentage, not how strong and powerful your mid-section is. While relatively low body fat percentage is a good thing in some cases (you don’t have to accelerate and move as much weight on the field or court), some athlete’s performances and recovery times may suffer if their body fat percentages were too low (<5%). Let focused training and nutrition dictate how aesthetically pleasing your body may become, not the other way around.
Wash-board abs may be “made in the kitchen”, but powerful mid-sections are made in training.