Commentary for Bava Kamma 14:7

We compare it to [a case of] a creditor. The Gemara was searching for a situation where we could apply the ruling of the cyclical change of price. The Gemara suggests that this could be true of a creditor. If his loan is collectable in Tishrai he is entitled to be paid from the middle quality fields of the debtor at the lower Tishrai prices. If he prefers to be paid with the lowest quality fields he must take them at the higher Nison prices.
The Gemara rejects this suggestion because this would have a negative effect on a person’s ability to obtain a loan. The lenders will not want to give loans, because the fact that he gave a loan is being used against him. If he had his cash in hand he would be able to purchase the poorest quality field at the Tishrai prices, now because he gave the person a loan he must take the field at Nison prices. This will discourage people from giving loans.
Tosafot wonders why the Gemara does not use the reasoning that it used earlier when the Gemara wanted to apply this ruling to a victim of damages. The Gemara said that forcing the victim to accept the middle or poor quality at Nison prices is weakening the position of the victim. The Torah says that he can collect from the finest and this ruling would in effect say that he cannot collect from the middle or poor quality at Tishrai prices. Why doesn't the Gemara use a similar reasoning here and argue that we are weakening the position of the creditor who can collect from the middle quality and you are saying that he cannot collect from the poorest quality if he so desires.
And the Gemara could not have asked, if so, that the creditor must accept the poorest fields at the higher Nison prices, you have weakened the position of the creditor, who is entitled to collect from the middle quality at the lower Tishrai prices and you are weakening his position by ruling that when collecting from the poorest he must accept them at the higher Nison prices.
Assuming that the Torah wanted to strengthen the creditor’s ability to collect his debt from the middle quality, the ruling that he must take the poorest quality at higher Nison prices is weakening his position.
However, this argument is incorrect because the Torah never strengthened the power of a creditor as it does the power of a damages victim; rather the reverse is true his position is weak because according to Torah law the rule of the creditor is to collect from the poorest. The Torah was not concerned that the creditor is in a weak position, so that would not stop us from forcing him to accept the poorest at Nison prices. It is only because it would discourage potential lenders that we do not force a creditor to accept the poorest at Nison prices.

Give me slightly more land of inferior quality. While the Gemara is searching for a situation where it can apply the cyclical change of price rule, the Gemara suggested that it might be speaking about a creditor who instead of taking one acre of middle quality fields wants an acre and a half of the poorest quality. At this point the Gemara believes that he can be forced to accept the poorest quality field at the higher Nison prices. There was a text in the Gemara that the creditor might be asking for a half acre of the prime quality and that he must accept that at higher Nison prices. Tosafot rejects that version of the Gemara.
We do not have the text: or if the creditor wanted a bit less of the finest.¹The Rosh does cite this text. See Pilpula Charifta note 8. If we had this text the Gemara would then be saying that we do give him a half acre of the finest but at the higher Nison prices. For if that were so, why does the Gemara ask in response to the suggestion that we are dealing with a creditor who wants a bit less of the finest: if so, that you force him to take the finest at the higher Nison prices, you are locking the door in the face of borrowers who will not be able to obtain a loan if we force the creditor to accept the finest at the higher Nison prices. This would make sense if the creditor had a right to demand the finest and we would say that you must accept the finest at the higher Nison prices, but since it is not at all his right to collect from the finest, theoretically the debtor can ask for any price he wants for the finest even more than the Nison prices, allowing the creditor to receive the finest at the Nison price is actually improving the position of the creditor, for it is established that the creditor’s rule is to collect from the middle quality and he has no right at all to demand the finest.