At issue: Mayberry, Frandsen and Ruf are all righthanded hitters.
With backup catcher Will Nieves (also a righthanded hitter) and Freddy Galvis (a switch-hitting defensive specialist) all but locks for bench jobs, one of the remaining three spots would almost have to go to a lefthanded hitter to give the bench balance. Manager Ryne Sandberg acknowledged as much yesterday afternoon, following the team's first full-squad workout of the spring.
"A lefthanded bat is necessary and needed there," Sandberg said.
Bobby Abreu entered camp as the odds-on favorite for that job. Although he turns 40 next month and didn't play in the big leagues in 2013, Abreu is a career .292 hitter with a .396 on-base percentage.
After rebooting his playing career in Venezuela this winter, Abreu will get to prove he can handle the job.
Where does that leave Mayberry, Frandsen and Ruf?
From the most logical of viewpoints - helping the team win - Ruf would seem to be the first in line for a major league bench job.
Ruf, 27, will work at leftfield and first base this spring, positions where Sandberg thinks he could earn as many as 300 at-bats this season in part-time duty. It's not difficult to figure why Sandberg would like to make that happen.
Only two major leaguers, Miguel Cabrera and Alfonso Soriano, hit more home runs last August than Ruf, who hit nine in 29 games. Overall, Ruf hit .247 with 14 home runs and 30 RBI in 73 games; his .348 OBP was tied with Chase Utley for the team lead among players with at least 250 at-bats.
But, the Phillies also have the most flexibility with Ruf: He can be optioned to the minor leagues. Both Mayberry and Frandsen have guaranteed major league contracts and no minor league options remaining.
Mayberry, 30, has found a niche on the roster for the last three seasons for his ability to play centerfield, the position where the Phillies have the least depth on the 40-man roster.
But Mayberry isn't viewed as a plus defender in center. And he struggled offensively last season, hitting .227 with a .286 OBP, 11 home runs and 39 RBI in 383 plate appearances.
"I didn't use the whole field as much as I could have [last] year, I got a little pull-happy," said Mayberry, who avoided arbitration with a 1-year, $1.5875 million deal last month. "[This winter], I worked on staying more closed [in my stance], staying square to the ball. That'll allow me to stay on the ball and cover more of the strike zone."
If Mayberry doesn't make the roster, the Phillies would still owe him his entire salary unless another team claimed him off waivers. If Mayberry does move on before Opening Day, nonroster outfielder Tony Gwynn Jr. could play centerfield at Triple A Lehigh Valley and jump into a starting role should Ben Revere get injured.
Sandberg said others on the big-league roster can play the position, including Marlon Byrd and Domonic Brown. Cesar Hernandez, a natural second baseman, will also continue to work in center, a position he began playing last summer.
Hernandez also could be Frandsen's main competition for a bench role. With Galvis in line as the sure-handed backup at shortstop, second and third base, Hernandez and Frandsen are competing for infield reserve jobs, along with nonroster players Reid Brignac and Ronny Cedeno.
Frandsen, 32, should have a leg up on the competition for two reasons: the guaranteed, $900,000 salary he is owed and the fact he led all major leaguers with 14 pinch-hits in 2013. Frandsen hit .234 with a .296 OBP overall last season, his first as a professional in a reserve role, after batting .338 with a .383 in 55 games with the Phillies in 2012.
"You can't justify the 2 years in my mind," Frandsen said. "One year you're playing every day . . . the next you're going a week, 2, 3 weeks without a start, and facing closers. I'm just gearing up to be the best bench guy here. The guy that - I felt like - that [former manager] Charlie [Manuel] and Ryno counted on in late-game situations facing closers. I don't know too many other guys here that were doing that last year."
A lot can change in the next month. Injuries and trades could open up roster spots. A spring rarely goes by without an injury, especially in Clearwater.
But if Mayberry, Frandsen and Ruf remain, the competition should be as interesting as any other in camp.
"Ultimately, at the end of the day, it's not secret," Mayberry said, "whoever is showing the best, playing the best is going to get the role."
On Twitter: @ryanlawrence21