The short answer: "1,500 at-bats or 500 games ... that's when you know if you have got an everyday, big league catcher," Simmons said. "Or if you have a backup or a marginal platoon guy."
Simmons has seen growth in the past year and a half he's been working with Hundley -- who entering Wednesday's game against the Rockies, has 611 career at-bats and 176 games behind the plate.
But Simmons isn't ready to give a complete grade yet, even though he's seen some very good things on the defensive end from Hundley.
"There's no question that he is growing. We are all seeing wonderful progress. When I first came here last year, everything he did was in fast motion. ... Everything that was thrown to him, he caught, tried to transfer and throw in what looked like fast motion," Simmons said.
"He has slowed down considerably."
The Padres want Hundley to be quick, but not fast, with his defensive mechanics. They have seen inroads toward that end, even as recently on their 5-1 road trip to St. Petersburg and Florida last week.
"I've tried to slow down and be smoother, be calmer," Hundley said. "Teddy and I have worked tirelessly on slowing it down and working on mechanics."
On that trip, Hundley threw out three baserunners in critical situations. All told, Hundley has thrown out eight of 34 would-be basestealers (23.5 percent). A year ago, Hundley was 10 of 66 (15.2 percent).
Simmons said he's seeing a much better prepared catcher, someone who is getting more comfortable with the league and opposing hitters and baserunners. That information has led Hundley to build what Simmons calls a database.
"All that fast motion comes from uncertainty -- who is this hitter, what does he like, what pitches does he like, not like, who is the pitcher, what does he throw and what pitches can he command? All of those anxieties create uncertainties, especially with young catchers because there's so much that has to be crammed in," Simmons said.
"You're seeing a much more comfortable defensive player now, someone who is learning the hitters, who knows his pitchers. He's incorporating all this data in his database so that in action, he can draw on it and draw on it quickly."