The Bayern Munich winger and Inter playmaker have been missing for their clubs recently, and have been forced out of the national squad for October's internationals
The veteran coach will have to make do without the services of star players Wesley Sneijder and Arjen Robben, while Tim Krul and Jetro Willems are unavailable due to physical problems, too.
Other notable absentees are Paris Saint-Germain defender Gregory van der Wiel and Manchester United's Alexander Buttner.
"Van der Wiel doesn't get enough playing time yet at PSG, and Van Rhijn and Janmaat are doing a good job in his position. Buttner needs regular match action, too," commented Van Gaal.
Rafael van der Vaart, Ibrahim Afellay and Nigel de Jong were left out of the Netherlands squad that saw off Turkey and Hungary in their opening qualification matches, but return to the team again.
Van Gaal's men currently occupy second place in Group D, level on points with Romania, having both taken maximum hauls from their first two encounters.
Netherlands host Andorra on October 12, before travelling to Romania four days later.
|Ricardo van Rhijn||Ajax|
|Ron Vlaar||Aston Villa|
|Bruno Martins Indi||Feyenoord|
|Urby Emanuelson||AC Milan|
|Rafael van der Vaart||Hamburg|
|Nigel de Jong||AC Milan|
|Robin van Persie||Manchester United|