The Japan star returned from international duty yesterday (Friday) to train with his Baggies team-mates for the first time in three months following a successful spell at Cardiff.
And Robson instantly laid down the gauntlet to the 25-year-old midfielder, who figured in Japan's 1-0 World Cup qualifying victory over Bahrain in midweek.
"Ina trained with the first team Friday morning after coming back from international duty," said Robson.
"I had a chat with him and said it was difficult for myself and Nigel Pearson to judge him when we first came here because he was coming back from a long-term injury and hadn't played any games.
"That was the reason I sent him out to Cardiff, so he would come back fitter.
"He looked a lot sharper than three months ago - and that's only after one training session.
"I've told Ina he's part of the squad now and it's up to him to prove to me he can get a place in the team.
"We've got a couple of months before the end of the season and I'll be judging Ina over that period to see whether he will be part of my plans for next season."
[West Bromwich Albion Official Site]
