The 30-year-old joined the Saints from Belgian side Genk two seasons ago but struggled for minutes under Ruben Selles and Russell Martin.
Seeking more playing time, the striker joined Trabzonspor on loan last season and made a significant impact, scoring 17 goals and providing four assists in 25 matches.
Despite showing keen interest in securing him permanently, the Turkish side were unable to reach an agreement with Southampton during the previous negotiations.
However, with injuries depleting their attacking options this season, the Black Sea Storm are keen to revive the deal to bolster that department.
Trabzonspor president criticises Southampton's approach to negotiations
Club president Ertugrul Dogan has expressed his dissatisfaction with Southampton's handling of transfer discussions for Onuachu.
Speaking to Turkish outlet A Spor about the club's winter transfer plans, Dogan highlighted the difficulty in reaching a deal for the striker, as the Saints continued to raise their asking price, making negotiations increasingly complicated.
"We had an agreement with Onuachu. We are still in contact. Southampton initially asked for €7m, which we matched. Then they raised it to €10m, so we went up to nine with bonuses, and then they increased it again to €15m," he stated.
"So, it became clear they did not want to sell him to us. We will not force a transfer. If the terms do not suit us, we will look elsewhere."
Southampton's reluctance to sell may stem from their own squad needs, especially after Onuachu played a crucial role in their recent 2-1 victory over Ipswich Town, scoring the winning goal.
Could Onuachu leave Southampton on deadline day?
While the Saints have not entirely ruled out a transfer, their firm stance on the fee remains an obstacle for the deal to go through.
Additionally, Onuachu's position on the matter remains unclear, as neither he nor his representatives have issued any public statements regarding his future.
Trabzonspor, however, still have a window of opportunity to complete the deal even after the close of the window tonight given the extension of the transfer window in Turkey.
While the English transfer deadline is February 3, the Turkish window remains open until February 11, giving them more time to negotiate.
However, securing the striker's signature may require a significantly higher bid as Southampton have made clear from the start.
Written by
Joshua Cole