19:00 BST, Saturday 30th June, Fisht Olympic Stadium (Sochi, Russia), ITV1
A 3-0 victory over Russia ensured Uruguay won all three of their group games and topped the group for the fifth time in their history - 1930, 1950, 1954 and 2010 - without conceding a single goal, the first nation to do so since Argentina in 1998.
Their performances, however, have not been representative of a side whose record suggests they may well go on to win the World Cup. In their opening game, for example, they needed a last-minute header by Jose Gimenez to give them the victory over Egypt.
Saudi Arabia put up quite the fight and Luis Suarez only managed to net once against the team that shipped five to Russia, whilst their most convincing performance came against the hosts.
Portugal gave us the game of the group stage when they drew 3-3 with Spain thanks to a Cristiano Ronaldo hat-trick, but Fernando Santos' side settled into themselves following their opening game drama and narrowly beat Morocco 1-0 thanks, again, to Ronaldo, with the Lions of the Atlas putting them under significant pressure.
With Spain also on four points and Iran on three, there was everything to play for when Portugal faced Team Melli in their final game and they progressed to the last-16 by a matter of inches, with VAR denying them three points and top spot as they were condemned to a 1-1 draw.
Overall, both sides are expecting to progress further than the last-16 which is what makes this tie even more tantalising.
Last Time Out
Uruguay 3-0 Russia
Russia were 2-0 down before they had Igor Smolnikov sent off on 36 minutes, and from that point, Uruguay cruised to a very comfortable 3-0 victory. Luis Suarez set them on their way after ten minutes as he drilled a low free kick past Igor Akinfeev in the Russia goal.
One of the stars of the tournament scored next, but Denis Cheryshev netted in the wrong goal to give Uruguay a 23rd-minute two-goal lead, when Diego Laxalt's 25-yard effort deflected off of him. It left Akinfeev in the unfortunate position of having conceded three goals without making a save.
Smolnikov made matters worse for the Russians as he received his marching orders for two avoidable bookings in eight minutes, but the hosts did regain some semblance of control early in the second half, with their best chances falling to Artem Dzyuba and Fedor Smelov.
Edinson Cavani had the last laugh and netted his first tournament goal in the 90th minute. The cherry on the cake for Uruguay and the statement victory Oscar Tabarez had been looking for.
Portugal 1-1 Iran
VAR was the star performer in this game, but for all the wrong reasons as bad decisions dominated the post-game rhetoric.
Ricardo Quaresma looked to have sent Portugal on their way to a second victory and top spot in Group B, with a classic Quaresma goal - a sensational outside of the boot finish from distance.
Cristiano Ronaldo was then at the centre of attention after his protests were waved away by the official following a foul in the area, though this was eventually awarded on review. With Ali Beiranvand saving the subsequent penalty, Iran were inspired.
Iran probed for an equaliser but generally struggled while Portugal looked comfortable with their one-goal lead, though their position could have been compromised when Ronaldo received only a yellow - after a lengthy VAR review - for an elbow on Morteza Pouraliganji.
However, with minutes to spare the referee, Enrique Caceres, waved away a penalty appeal for Iran only to see VAR put it under review. He then watched the incident and somehow deemed that Cedric had handled the ball.
Karim Ansarifard converted the spot kick to give Iran a slim hope of qualifying though it was not enough as Portugal got the point they needed, with Mehdi Taremi hitting the side netting in stoppage time.
Uruguay have no injury concerns heading into this fixture, but they are likely to reunite Atletico Madrid duo Diego Godin and Jose Gimenez - in place of Sebastian Coates - who missed the final group game.
Uruguay played in a 3-5-2 formation, which heralded their best performance of the tournament, which may see Tabarez stick with the system in favour of the previous 4-4-2.
Portugal have the luxury of being able to play the same side that drew with Iran last time out.
Joao Moutinho is likely to return to the starting XI in place of Adrien Silva after missing out against Iran, with Andre Silva keeping his place up top with Ronaldo.
After his match-winning strike against Iran, Ricardo Quaresma could retain his place over Bernardo Silva, though he could be shifted to the left in place of Joao Mario to accomodate Bernardo.
Key Battle: Luis Suarez (Uruguay) vs Cristiano Ronaldo (Portugal)
These two stars will most definitely have a say on the result of this match and you have to wonder if the fate of this game lies on which one of them can take their chances.
Both players are more than capable of winning a game on their own and there is also the added storyline that they play for the rival El Clasico teams - Barcelona and Real Madrid.
Ronaldo currently has four goals at the World Cup, and he made headlines with his hat-trick in game one against Spain, though he has gone a little quiet since.
Suarez, by contrast, has improved with each passing game and has two goals at the tournament, one against Saudi Arabia and a clever free-kick to open the scoring against Russia.
This is the Portugal of South America against the Uruguay or Europe, hence a truly cagey affair with little clear-cut chances falling by the way of Suarez and Ronaldo.
This will be a game of moments, likely a piece of magic the difference between the two sides, which makes Suarez and Ronaldo - the difference-makers - all the more important.
Doing another Portugal
In 2016 few people would have tipped Portugal to win the European Championships, but they did. They somehow defended their way to a victory and they actually only won one game in 90 minutes in the whole competition.
Could they do it again?
Defensively they will need to improve - with Pepe and Jose Fonte now two years older and Raphael Guerreiro proving a liability - but there is no reason why this team can’t use the experience of 2016 to defend their way to another unlikely victory.
It's the tactic they have employed in the group stages, even against unfancied nations like Morocco and Iran, but they will need to improve the quality of their counter-attacks to find a way past Diego Godin and Jose Gimenez.
The new Uruguay
Despite their reputation as perennial outsiders for major honours, Uruguay have failed to win over those on the fence with three fairly drab performances.
Two 1-0 victories over some of the worst nations in Russia did little to bolster their perceptions, but a more convincing win coincided with a change in system.
From a 4-4-2 to a 3-5-2, Oscar Tabarez has kept the Cavani-Suarez partnership intact, but given Matias Vecino and Rodrigo Bentancur more licence to create in the final third with the addition of a defensive midfielder to sit behind them.
This was, arguably, their biggest criticism in their first two fixtures, with Vecino and Bentancur struggling to impact the game as they had to balance both defensive and offensive duties. Lucas Torreira shoulders this responsibility and, thus, La Celeste looked far more creative against Russia.
Prediction: Uruguay 1-0 Portugal
Uruguay are an impressive defensive unit and they have the ability to keep Ronaldo and Portugal quiet, especially with a five-man defence now providing even more protection to an already solid back four.
This game will be decided on a moment or a mistake. Both teams are cagey, play pragmatic, defensive football and expect their star players to create a moment of magic. Uruguay should just about have enough to get past their counterparts without conceding their first goal.
Listen to the RealSport football writers discuss all the action from Day 15 of the World Cup in Kremlins in the Basement: RealSport’s daily World Cup podcast.