Rui Jorge's side are currently bottom of the section on one point, while Belgium currently sit second, picking up two points from their opening two games of the tournament.
Match preview
Portugal have never won the European Under-21 Championship, but they have made the final of the competition on three separate occasions, most recently in 2021, when they lost to Germany.
The national side are facing a battle to reach the quarter-finals of the 2023 tournament, though, having made a disappointing start, picking up only one point from their first two matches in Group A.
Jorge's team opened their tournament with a surprise 2-0 loss to Georgia Under-21s before playing out a 1-1 draw with the Netherlands Under-21s on Saturday, with Brian Brobbey cancelling out an opener from Andre Almeida.
A win for Portugal in this match would move them level on four points with Georgia, but the Group A leaders would finish above them at the head-to-head record.
As a result, Portugal need to beat Belgium and hope that Georgia overcome Netherlands in order to claim second position in the group and a position in the knockout round.
Belgium are currently second in the section, opening their tournament with a goalless draw against the Netherlands before drawing 2-2 with Georgia on Saturday.
Jacky Mathijssen's side led 2-0 against Georgia courtesy of goals from Maxim De Cuyper and Largie Ramazani, but the group leaders managed to fight back to secure a share of the spoils.
Belgium would be through to the knockout round if they win on Tuesday, while a draw would also be enough if Netherlands fail to overcome Georgia in the other match in the section.
The national side's best-ever performance at a European Under-21 Championship came in 2007, reaching the semi-finals, but they surprisingly failed to qualify for the 2021 edition of the tournament.
Portugal Under-21s European Under-21 Championship form:
L
D
Belgium Under-21s European Under-21 Championship form:
D
D
Team News
Portugal's squad is full of quality and experience at the highest level, with Nuno Tavares, Almeida, Pedro Neto and Fabio Silva among the standout names in the squad.
Head coach Jorge has big decisions to make in the final third of the field, and it would not be a surprise to see Fabio Silva potentially drop out of the XI, with Henrique Araujo being introduced.
Diego Moreira and Francisco Conceicao are also battling to be involved from the first whistle, and the Portugal bench could play a crucial role in Tuesday's contest.
Tomas Araujo is also available for Jorge after being suspended for the team's last match.
Belgium, meanwhile, will again have Lois Openda at the tip of their attack, with the Lens forward scoring 13 times in 17 appearances at this level of football.
Ramazani was on the scoresheet against Georgia and should retain his spot in the final third, while there will be a start for AC Milan's Charles De Ketelaere.
Hugo Siquet will again feature at right-back for Belgium, and Mandela Keita is also likely to be given the nod in central midfield despite the competition for positions in that area of the field.
Portugal Under-21s possible starting lineup:
Biai; Ze Carlos, Penetra, Amaro, Tavares; Neves, Dantas, Costa, Almeida; Neto, Araujo
Belgium Under-21s possible starting lineup:
Vandevoordt; Siquet, Debast, De Winter, De Cuyper; Vranckx, Keita; Ramazani, De Ketelaere, Balikwisha; Openda
We say: Portugal Under-21s 1-0 Belgium Under-21s
Portugal have struggled in the competition thus far, but we are backing them to win on Tuesday, which would leave them in a position to potentially qualify for the quarter-finals of the competition.