Today, we did more with catching, and this time I used a new object. For this session, we played with a black and white baseball.
Immediately, I noticed a more keen reaction to the ball. Perhaps the different colors on the ball made it easy for him to track the baseball's movements. With the disc, sometimes it seemed he couldn't pick it up very well.
It may be a height issue as well. With the ball, I throw it underhand, so it may enter and stay within his vision for longer time, helping him track it in the air. Whatever the reason, he was going after it aggressively in the air.
He has a harder time grabbing it, sometimes it pops out of his mouth, or he misjudges it, and it bounces off his nose. Sometimes, I swear he's trying to catch it with his paws! He seems to be coming up with a way to catch it more reliably, by moving towards it a bit. Perhaps he's trying to understand how to catch the ball at it's highest point.
His enthusiasm is still strong when I do shorter tosses (short as in: about a foot from him, if that). He jumps up high, sometimes making a twisting landing. He hangs on to the ball, though, and I started doing some of those tosses in more rapid succession. He liked doing these, so I'll definitely do more with him. These shorter tosses are easy to do indoors as well, making for more chances to practice.
I've considered using a smaller ball (like his tiny soccer ball) so it's easier to catch, but then again he can catch this ball. He just has to learn to judge it and adjust to the throws.