Both Inacio and Todibo have been strongly linked with a move to Old Trafford in recent months, with the Red Devils allegedly keen to recruit a new central defender in the New Year.
Inacio has developed into an integral first-team player for Sporting Lisbon since emerging from the club's academy that he joined at the age of 11, making a total of 133 appearances in all competitions.
The 22-year-old, who has also been linked with Liverpool, has won one Primeira Liga title and two Taca da Liga trophies with Sporting, and he is understood to have caught the eye of a number of clubs during outings in the Champions League and Europa League in recent seasons.
As for Todibo, he has blossomed into a key player for French outfit Nice over the last two years following an unsuccessful spell at Barcelona.
The 23-year-old Frenchman has featured in 111 games for Nice and was a standout performer for the Ligue 1 club last season, starting 33 of his 34 top-flight appearances.
Rumours of Man United wanting to reinforce their options at the back come at a time when Harry Maguire continues to be linked with a move away from the club, while both Raphael Varane and Lisandro Martinez have struggled with injuries so far this season, leaving the Red Devils light in defence.
According to Football Insider, Man United initially registered their interest in both Inacio and Todibo as they scouted the market for a new centre-back after failing to bring one in during the summer.
However, the report adds that the Red Devils have now decided to pull the plug on a proposed swoop for either defender, as the club have limited resources and are unable to spent big on new recruits in the winter window.
It is understood that Erik ten Hag's side could now shift their focus to signing a low-cost alternative to their top targets including the likes of Inacio and Todibo.
Football Insider claims that one of those alternatives could be Uruguayan defender Sebastian Caceres, who Man United are said to be closely monitoring along with several other clubs including Tottenham Hotspur, Newcastle United, West Ham United and Fulham.
Caceres plies his trade in Mexico with Club America, where he has spent the last three years and made 109 appearances as a centre-back in all tournaments.
It is claimed that Club America are not expected to demand a significant price for the 24-year-old, who is out of contract in December 2024.