Tau has lost his place in the Club Brugge starting eleven due to struggles with his fitness and was recently sent a warning by manager Phillipe Clement.
Ntseki expressed his worry about players struggling in Europe as they are needed in the national team for important World Cup qualifiers coming up in March.
"Look, it's a worry for every player you have in Bafana Bafana if he's not playing at club level. It becomes an issue. It becomes a problem," Ntseki said.
"Because you want to see your players playing regularly, you want to see players effective in the game wherever they are. You want to see your players defending in terms of their defensive role and scoring or assisting goals."
The coach feels Tau overloaded himself during the first rounds of the UEFA Champions League and national team matches, which might have put too much strain on him with the pressure to deliver as one of the trusted players in the team.
"If you have a player who is not playing you become worried, and in this case I think he overloaded himself by playing in the UEFA Champions League and being in the national team trying very hard," Ntseki explained.
"The game we played against Ghana away and the one we played with Sudan at home, if you look at the programme in playing those matches it took a lot of energy out of a lot of players. Most of them struggled when they went back to their teams overseas.
"Because South Africa is different. If you are from Ghana it will be less than six hours to any European country where you are playing. But of you are in South Africa it's 12-plus hours to get to your team, so the travelling itself and the load that you put into your game also affects some of our players."
However, Ntseki believes the former Mamelodi Sundowns star will bounce back in time for Bafana's important fixtures in March.
"I think he's a professional. I can tell you now that wherever he is, he is working very hard to get to that level because he's a very disciplined individual who is committed to the game."