Boro are in the midst of a defensive injury crisis with George Edmundson, Rav van den Berg, Luke Ayling and Darragh Lenihan all currently unavailable.
Pieters has spent part of the last week training with Boro’s first-team squad, with Michael Carrick and the rest of the Teessiders’ coaching staff assessing the defender’s fitness levels.
Pieters was released by West Brom last summer when his contract at the Hawthorns expired after two years as a Baggies player.
He joined Luton Town as a free agent on a short-term deal last December, but did not make a single senior appearance for the Hatters before he was released after around a month.
His last senior appearance for anyone came just under a year ago when he played the first half of West Brom’s 2-0 win over Bristol City in March 2024.
Predominantly a left-back during most of a career that saw him have successful spells with Stoke City and Burnley, Pieters can also play at centre-half.
It remains to be seen whether Boro opt to offer him a deal, with the Teessiders having 11 more Championship games to play this season, starting with this afternoon’s game at Swansea City.