CLEARWATER, Fla. - Ethan Martin finished an early-morning workout, and while his teammates checked in and put on their home uniforms, the pitcher changed out of his baseball uniform and into street clothes.

Shortly after the 24-year-old Martin left the building, he was stopped by one of his bosses. General manager Ruben Amaro Jr. patted the pitcher on the back and wished him well.

Martin was off to get an MRI on his ailing right shoulder. On his way to the parking lot Martin passed 23-year-old Jonathan Pettibone, who was throwing off the mound for the first time in nearly 2 weeks after his own bout with shoulder discomfort.

Neither young pitcher was guaranteed to be on the major league roster when the season begins, but both play equally important roles in the overall pitching depth that is vital to a baseball team's success.

Beyond likely Opening Day starter Cliff Lee and veteran Kyle Kendrick, who allowed three runs in two innings in his spring debut yesterday, the Phillies have:

* Cole Hamels, who isn't likely to pitch in a spring game for another 10 days or so.

* A.J. Burnett, who hasn't pitched in a game yet, either, but his scheduled to do so tomorrow.

* Roberto Hernandez, who was demoted from Tampa's rotation last summer after sporting a 5.00 ERA in 23 starts.

* Miguel Alfredo Gonzalez, who might be the single biggest mystery in any major league camp, since he hasn't pitched professionally in almost 3 years, according to Amaro. Gonzalez is scheduled to pitch in relief in today's game against the Yankees in Tampa.

"It's always a concern," Amaro said of the state of his starting pitching depth.

Since neither Hamels nor Pettibone is likely to be ready by the first week of April, the Phillies' projected five-man starting rotation is really only four players deep: Lee, Burnett, Kendrick, Hernandez. Because you really can't think it's realistic to throw Gonzalez into a major league game in a month after looking rather rusty in light work so far this spring, can you?

"Oh, I think it's realistic, yeah," Amaro said of Gonzalez, who signed a 3-year, $12 million with the team as a Cuban free agent in August. "A lot of it depends on how he performs, how ready he is. But I don't have any time frame for the guy."

The Phillies current time frame is 4 weeks and 2 days: that's when the regular season begins. The only other starting pitchers in camp, beyond the aforementioned veterans and injured righthanders, are:

* David Buchanan, a 24-year-old who has made only six starts beyond Double A.

* Sean O'Sullivan, a 26-year-old, nonroster lefthander who has a 5.89 ERA in four seasons with the Padres, Royals and Angels.

* Jeff Manship, a 29-year-old with a 6.42 ERA in five seasons with the Twins and Rockies.

* Jesse Biddle, the organization's 22-year-old top prospect, who Amaro has already said has no chance of breaking camp with the team.

But the Phillies are confident in Hamels' progression and are apparently OK with a patchwork approach to the tail end of the rotation.

"It's a little early," Amaro said of reason for concern. "I'm not going to do anything about it right now except wait and see how things shake out. We have [those] guys that are here in camp. If we have to create depth some other way, we'll do it . . . This is part of the game."

But the reality is the calendar turned to March overnight and the Phillies can barely put together five healthy arms for a rotation, let alone the actual number it takes for a major league team to get the 162-game, 6-month season.

In 2013, 30 major league teams utilized 308 starting pitchers, an average of a little more than 10 per team. All of those teams also used at least eight different pitchers for five or more starts last season.

Although some teams get lucky - the Tigers used only six starters in 2013 - the vast majority of teams rely on a lot more than the five guys penciled in at the start of each season.

The Pirates reached the playoffs thanks in part to pitching depth: Twelve pitchers made at least one start, nine of them made five or more starts. Ditto the Dodgers: Eleven pitchers started a game, 10 of them started five or more games.

"I think you always have to look for starting pitchers," pitching coach Bob McClure said, "whether you're perfectly healthy or not."

The Phillies are not perfectly healthy. Amaro said yesterday that he's content in letting what he already has in camp play itself out.

At least there was one encouraging sign for the general manager: Minutes after Martin was off for the doctor's office, Pettibone walked off the mound after a 20-pitch session and said he was "back on track" following a 2-week spring hiccup.

"That was like the first steppingstone and I cleared that," Pettibone said. "Now it's 'Game on.' "

Pettibone, who missed the final 2 months of last season with shoulder issues, will likely throw his second bullpen session tomorrow or Monday.

Phillers

Darren Daulton watched yesterday's game at Bright House Field. Daulton, who was diagnosed with brain cancer in June, will take part in an on-the-field tribute to late, former Phillies manager Jim Fregosi before the Phillies host the Atlanta Braves on Wednesday . . . Phillippe Aumont bounced back from a shaky spring debut to retire all three batters he faced yesterday, although his first pitch clanked off the backstop. "I liked him throwing his fastball and sticking with it," manager Ryne Sandberg said. "He doesn't have to throw his breaking balls right now. Pound the zone with the fastball, thats when he's effective" . . . A.J. Burnett will make his Phillies debut tomorrow at Bright House Field against his most recent former team, the Pittsburgh Pirates (1:05 p.m., Comcast SportsNet).

On Twitter: @ryanlawrence21

Blog: ph.ly/HighCheese