Don't want to give too much away, but I know this injury pretty well. With the way he was moving on it in the game, (especially lateral motion and weight-shift), I can say with about 95% surety that he didn't tear his meniscus, but most likely strained it.
There are actually two menisci between the tibia and femur, and very often the injury involves both. One problem with this injury is that it's easy to re-injure it, and with each additional injury, the range-of-motion of the patient becomes more and more limited, with the build-up of scar tissue. Even with a strain it should be treated quickly and thoroughly with the old "RICE" standby, (rest, ice, compression, and elevation).
Therapeutic ultrasound is also a key tool in reducing inflammation, which is the key to healing the meniscus. It depends on the physician, but while there are some miniscus injuries that can be "played through", by the look of his initial reaction and pain, if it is truly his miniscus, most doctors would recommend staying off it as much as possible.
Another draw-back is that there is very little blood circulation to the menisci, which makes healing very slow, unfortunately. Compression and ultrasound work to increase blood circulation to the area and speed up the healing process. There has also been a lot of promising work done with electrical stimulation with such soft-tissue injuries, but not widely used as yet.
Personally, I'm hoping it's just a knee contusion, because even a sprain or strain of the meniscus can mean a lengthy healing process.