Robben underwent treatment in the Netherlands and joined the team in Johannesburg last Saturday but had been training on his own until Friday.
"This was his first complete training since we got together and that is something, " coach Bert van Marwijk told a news conference at the Moses Mabhida Stadium in Durban.
"Now we have to wait to see how his hamstring reacts tomorrow morning but in normal circumstances he would not play against Japan."
Netherlands and Japan both registered opening wins against Denmark and Cameroon respectively in Group E and have not many secrets from each other.
Both teams played each other in a friendly in September last year, which was won by the Dutch 3-0, although Japan dominated the first hour.
Van Marwijk, however, expects a different Japan, also based on the defensive style they showed in the match against Cameroon.
"They have been searching for a tactical style that would suit them and played many friendlies which they lost," Van Marwijk added.
"But they seemed to have found it and you always have to be ready when the tournament starts and that is exactly what they were."
During the first week of the tournament the Dutch built an impressive list of complaints including the vuvuzelas, the pitches, the ball and the altitude in Johannesburg.
The move to Durban, which is at the coast at sea level, seemed to have solved the problem of the altitude and the Jabulani ball, but Van Marwijk proved creative in finding new issues.
"It is rather warm today and the forecast for tomorrow is that it will be even warmer, but we just have to deal with that," he added.
"It is a fast ball but after working with it you get used to it. But now we are playing on sea level and then it reacts normally," said the more positive Dirk Kuyt who scored the second Dutch goal against Denmark.
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