Ayala missed all of 2006 while recovering from elbow reconstruction surgery. The last time the 29-year-old played in a Major League game was on Sept. 22, 2005, against the Giants. He pitched only two games that month because of bone spurs in his right elbow. The spurs were removed after that season.
However, Ayala needed to undergo surgery again last March, after he hurt the same elbow pitching in the World Baseball Classic.
"Unless something changes dramatically, then Luis Ayala [will join] Nick Johnson and Mike O'Connor on the disabled list," general manager Jim Bowden said. "We are going to take the conservative approach with Luis. We are not going to rush him while he's coming back from Tommy John surgery.
"I can't put a timetable on it, but, look, I could be surprised. But we can't put him on the roster and not have him available to pitch back-to-back days. It's not fair for the team to do that. Although we have not made that final decision, as of now, that's where we are leaning toward."
Earlier in the week, Ayala had a bullpen session and threw breaking balls for the first time, and Bowden felt that Ayala looked to be about 75 percent of where he needs to be.
"We are pleased with the progress," Bowden said. "I just don't think it is Opening Day progress."
Ayala's absence was a huge blow to the Nationals in 2006. Outside of Chad Cordero and Jon Rauch, the team couldn't find a reliever who could work regularly. From 2003-05, the organization was used to Ayala appearing in at least 60 games and holding teams in check in the seventh and eighth innings.
If Ayala is placed on the disabled list, it would mean two things: Ryan Wagner and Rauch will be the setup men, and the Nationals will carry 12 pitchers on the 25-man roster.
"We are going to carry (12) because of our rotation," manager Manny Acta said. "We are probably going to need guys [who can start and relieve]."
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.