Nketiah emerged from the bench to net a late equaliser for Leeds at Preston to leave them second in the Championship.
Gunners legend Ian Wright took to Twitter to urge Bielsa to start the England Under-21 international after his third Championship goal of the campaign.
"We have never proved this kind of combination in our training," Bielsa said of the possibility of the strike duo playing in tandem.
"In the international break, Nketiah is not with us, because we play twice a week and when we prepare in the week there are few spaces to try these kinds of things.
"When you have a series of bad results and you have to find a different solution, that [kind of series] hasn't happened. I think that all this around Bamford and Nketiah doesn't help both of them.
"It is natural that people argue about my decision because they don't have all the reasons I have. I want both of them to be a success this year. We have 46 matches or 50 matches.
"We are in the first 25 per cent of the competition. I think that we have time so I can find a way that both of them shine. If this doesn't happen, it is going to be a mistake of mine."