Well, if it's not Naida, it must be Svanda. I've never stuck with her for too long, but her stats may very well develop better. That's what I like about the Blitzball, the best team when everyone's Level 1 is not the best team for when everyone's Level 99.
Speaking of which, the other recruit you can sign in the Calm Lands (near Yojimbo's cave) is Durren. He deserves an honourable mention for having almost a 30 catch stat at Level 1. I know people like to try and grab Nimrook from the Psyches, but until Level 12-15 or so, Durren is much much much better.
But by the time you can get Durren, you'd probably already have Miyu.
Durren's CA is 12 at Lv1. Nimrook is always the best at any given level but Durren comes within a point of him around Lv20 and stays there until Lv40. Durren's CA tops out at 30 at Lv50 and then falls back to 24 by the time he's Lv99.
Miyu is a much better choice.
The free agents I recruit are always Shaami, Kiyuri, Ropp and Naida.
My bad. I knew it was something to do with 30 that made him special.
So I suppose the official ruling ought to be if for some reason you don't get Miyu at Moonflow (like some other team got to her first), then get Durren if Nimrook is still with the Psyches.
I mentioned this before, but Kyou is a decent goalie as well. Better than Miyu at later levels I believe. Ditto Wedge.
I didn't play much blitzball but I always made sure to get rid off Datto as soon as possible and get Nimrook when I got the airship.
Datto is annoying at the beginning. He's not horrible, but the opposition goalie always seem to have the edge on him no matter what. But if you persist with him, teach him some skills, you'll find that he's one of the better forwards in the game. He develops blistering speed.
I normally get Wedge to be a forward, then give up on him when his shoot stat isn't good against anyone anymore. After this, I get Wakka.
I also get Ropp to be a defender, alongside Jassu.
Jamal is my catcher, when I reset after each league. If I am going for longer, I will keep Keepa.
And Brother makes an excellent Midfielder.
I keep the original team. After watching them in the story, it would rip me apart to seperate them. Besides (or should I say, Besaids! No) I never lose a game.
I keep the original team and hire Wakka when he's available. I only play enough to get his sigil though.
Kefka's coming, look intimidating!
Have a nice day!!