Defender Lopez and winger Miyaichi both featured in the Latics' Under-21s fixture against Nottingham Forest earlier this week as part of their rehabilitation from long-term injury lay-offs.
A substitute appearance in the 1-0 fourth-round win at Macclesfield in January is the only first-team action Lopez has seen since he suffered a hamstring tear in the 2-1 Barclays Premier League loss at Norwich in December.
Miyaichi, on loan at Wigan from Arsenal for the season, has been sidelined by an ankle problem, with his last involvement with the senior side coming in a substitute run-out in the 3-0 away league defeat to Liverpool in November - a game in which he was making his comeback from a groin complaint.
Asked this morning about the duo, Latics manager Roberto Martinez - whose squad has been hit by a host of injuries this season - said: "Adrian Lopez played 90 minutes for the Under-21s and Ryo played 45 minutes, so I do consider them fully fit and I think they are available now.
"Emmerson Boyce and Antolin Alcaraz have come through our two previous games, against Reading and Liverpool, well enough.
"So I do expect everyone to be available for selection apart from Ben Watson, Albert Crusat and Ivan Ramis. Probably this is the strongest we have been this season."