Preview: Northern Ireland's only victory will have them confident
When the Norther Ireland fans looked at their schedule in Group F, they more than likely did not expect to defeat Russia. The truth is that they currently find themselves fourth in the group with six points, having defeated the Russians, along with three draws against Portugal, Azerbaijan and Luxembourg.
The Green and White Army may not have the greatest chances of making it out of their group, but they at least are not going down without a fight.
A one goal draw in their first meeting with Portugal at the Estádio do Dragão was nearly a victory, if not for a late equalizer from Helder Postiga. The Valencia striker saved the day for Paulo Bento's squad in the 79th minute, cancelling out Niall McGinn's 30th minute goal.
On Friday, they will try to make things difficult for the Lusitanos once again, as Paulo Bento's side will try to keep their place in the top spot.
With an extra match played and a two point advantage over second placed Russia, the Portuguese can not afford any slip-ups. Fabio Capello's Russian side will square off against Luxembourg on Friday, which means that Portugal will know a victory is likely for their Group F rivals.
Paulo Bento has opted to call up a few new faces into the squad, which include Porto's Licá and Josué.
Given the number of injuries in the squad, Paulo Bento had no choice, but he will be fortunate his captain will be available on Friday. Hugo Almeida, goalkeeper Beto and Zenit St. Petersburg's Danny all had to leave the squad due to injury.
Real Madrid's Cristiano Ronaldo had missed training earlier in the week due to muscle problems, but at the moment, it appears as if he will be fit and available for their match at Windsor Park.
Having to deal with the Portuguese captain will not be an easy task, but Michael O'Neill is confident his squad is up for the task.
"He has the freedom to play wherever he wants on the pitch, and it is up to us as a team to stop him," the Northern Irish manager told reporters.
"At times it is not a matter of stopping him, but to limit his space. To do that, we will need good organization and a lot of work."
When these two sides first met in that 1-1 draw, O'Neill believes Ronaldo's lack of influence in the match was a result of his sides hard work.
"If we look at the match in Porto, I think the whole team was fantastic. We are going to need the same in Belfast. We need to always be cautious because when a player like Ronaldo gets space, he can cause a lot of problems," O'Neill added.
Another failed trip away from home, such as the one against Israel could cost the Portuguese. They will need to be patient, in order to break down the hosts, who will look to duplicate the performance from their first meeting.
Where to watch - live stream, start time, TV channels, live scores
Watch Northern Ireland vs Portugal Friday, September 6, 2013:
In the UK at 19:45 BST on: Sky Go, Sky Sports 4/HD
In the USA at 14:45 ET on: ESPN3
If you are outside of the viewing areas mentioned above, be sure to check the Northern Ireland vs Portugal match page for full TV listings.
