Bamford failed to find the net for the eighth match in a row at Preston North End on Monday but Nketiah, who replaced him in the second half, looped the late equalising goal in a 1-1 draw.
With Bielsa a big fan of the contribution Bamford makes in the build-up play, some fans would like to see Nketiah partner him, but Bielsa does not know if it will work.
"To play together they should play one behind the other," said the Argentinian. "This player would be Bamford, naturally.
"But we have never had the proof of this kind of combination in training. During the international break Nketiah was not with us and now we are playing twice a week.
"When we prepare for matches there are few spaces to try this kind of thing.
"All this talk around Bamford and Nketiah doesn't help either of them.
"If you listen to the supporters, one minute the people ask for Nketiah and then a second after they shout for Bamford.
"It's natural that people argue over the decision because they don't have all the evidence. Bamford is a great player and Nketiah is a great player."
Bielsa admits getting the best out of both players is a difficult task, but one he is determined to achieve over the course of the season.
"If just one of them has success this season I will not have taken advantage of the other but the process lasts for nine months and 46 or 50 games. We are only 25 per cent of the way through the campaign.
"We have to find a way for both of them to shine. If this doesn't happen it's going to be my mistake."
Nketiah's equaliser kept Leeds second in the table and with Barnsley holding West Bromwich Albion, the gap to the Championship leaders is still two points.
Nketiah's headed equaliser came from an 87th-minute free-kick, to the frustration of Preston manager Alex Neil.
"We didn't defend a set-play well enough and that's taken two points off us," he said. "We committed so many players to the wall that we were short at the back post.
"I'm disappointed we didn't win the game. Did we deserve to win it? I think the only way we deserved to win it was because we took the lead, not because we were dominant because I don't think either side was."