Despite being linked with World Cup winner and Borussia Dortmund star Mats Hummels for much of January, Louis van Gaal's latest bolstering at the back comes in the form of a 21-year-old left-back who has only played four games in the second tier of English football.
Kellett played at left midfield for much of his spell at Plymouth Argyle earlier this season, he is considered a left-back by trade and, if he gets his shot in the Red Devils first team, is expected to be deployed in defence.
Although Kellett lacks experience at the top level, he has an abundance of minutes played this season having played every second of 12 consecutive games for League Two midtable side Plymouth.
Kellett is the second young defensive signing for the lower levels of English football by Manchester United in the past week, who snapped up eighth-tier Salford City right-back Saqiq El Fitouri.
However, with the Red Devils facing competition from the likes of Southampton, Arsenal, Tottenham and Liverpool for a place in the top four, some fans are likely to be perplexed that more experienced dealings were not made in the mid-season window.
They were linked with Paris Saint-Germain centre-back Marquinhos on transfer deadline day but reports suggested that the Ligue 1 champions were stubbornly refusing to let go of the 20-year-old Brazilian they bought for €31.4 million in 2013.
Bolton have been recompensed for letting go of Kellett temporarily with Switzerland Under-19 international Saidy Janko heading to them on loan in return.
