Cueto's father, Domingo, has been ill, and Cueto has been absent from San Francisco's spring camp. He has been throwing bullpen sessions at home, but there is worry that Cueto won't have time to build up to 60 pitches in time to work amid the charged atmosphere of the tournament.
Peralta is in the designated pitcher pool for the Dominican Republic, and he is only expected to pitch during the first round of the tournament before returning to Brewers camp. The Dominican team has the Cardinals' Carlos Martinez and Marlins' Edinson Volquez among its other starting pitchers, and the team opens play on March 9 in Miami.
"They're probably going to let me know in the next few days," said Peralta, who will leave the Brewers on March 5.
In his first Cactus League start on Sunday during the Brewers' 10-8 loss to the Dodgers, Peralta worked around some command issues with help from catcher Jett Bandy, who threw out a pair of baserunners trying to steal second base. The second of Bandy's throws ended the inning as part of a double play after Peralta struck out Chase Utley.
In the second inning, Peralta walked Enrique Hernandez with one out but erased that with a ground-ball double play that brought his day to an end.
Peralta is hoping for a steadier 2017 after enduring a demotion to the Minor Leagues last season. He salvaged his year by returning in August with increased velocity and posting a 2.92 ERA over his final 10 starts.
Brewers pitching coach Derek Johnson, Triple-A pitching coach Fred Dabney and pitching coordinator Rick Tomlin all played a role in Peralta's refinement of mechanical changes over the summer, manager Craig Counsell said.
"Wily got to the place where he made the adjustment, and he got some velocity back," Counsell said. "And he was throwing his slider a little bit harder; did his slider improve, or did the velocity help the slider? That's a hard question to answer."
Peralta is eager to continue that process in 2017.
"It is a big season. I think I have to go back and have a good season," Peralta said. "My last two have been a little bit rough; I'm having a really bad first half [and] the second half has been better. My goal this year is to go into the start of the season really good.
"That's one of the reasons I want to be in the [World] Baseball Classic. It will be good competition early, and I think that's going to help me out."
Adam McCalvy has covered the Brewers for MLB.com since 2001. Follow him on Twitter @AdamMcCalvy, like him on Facebook and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.