The new manager is arriving at Old Trafford with the team in the relegation zone after a disastrous start to the Premier League season, and the club are understood to be prepared to accelerate plans to improve the squad.
A defender is reportedly the leading priority, with United having struggled to find adequate cover at left-back and needing greater depth in central defence.
The club had initially intended to address some of those issues during the summer, but their recruitment was focused heavily on other positions. The poor start to the campaign has increased the pressure to make changes before the end of the season.
Pochettino is expected to have an important role in deciding which players United pursue. Discussions over January recruitment formed part of the initial conversations between the Argentine and the club, with the new manager keen to influence the squad he inherits.
Manchester United have also been linked with attacking additions, including Como midfielder Nico Paz, although strengthening the forward line is considered more likely to be a priority for the summer.
The immediate concern is the defence. United have struggled for consistency and have lacked suitable alternatives in certain positions, leaving the club vulnerable when first-choice players have been unavailable.
Pochettino will be expected to assess those weaknesses before deciding where investment is most urgently required. The club's recruitment strategy has come under scrutiny during a difficult period, and the new manager will want a clearer understanding of how the squad can be improved.
The former Tottenham and Chelsea coach has a reputation for developing younger players and working with academy talent, but he will also need experienced players capable of helping United recover quickly.
There has been speculation over possible departures as well as arrivals, with the futures of several senior defenders likely to be assessed once Pochettino has worked with the squad.
United's financial backing in January will be important, although no specific budget or transfer agreement has been confirmed. The club have spent heavily in recent windows, and any further investment will need to be directed towards players who fit the new manager's plans.
Pochettino is due to begin work at United on November 18, with his first match expected to be the Premier League meeting with Liverpool at Anfield on November 22.
The scale of the task is clear. United need results immediately, but the January window could provide Pochettino with his first opportunity to reshape a squad that has struggled to meet expectations.