The Kawasaki kingpin goes into the final European round of the series trailing Toprak Razgatlioglu by 20 points after his Pata Yamaha rival sealed a double last weekend at Jerez in Spain.
Rea finished as the runner-up behind Razgatlioglu in race one but could only manage fifth in the second encounter, when he struggled with a lack of rear grip with the softer option tyre in the hotter afternoon conditions.
The 34-year-old boasts a formidable record at Portimao, where he has won 12 times during his career. Only Assen has yielded more success in terms of outright victories for Rea, who brought his tally up to 15 following a treble at the iconic Dutch TT circuit in the summer, surpassing Carl Fogarty’s record of 13 wins.
With two rounds remaining after this weekend in Argentina and at the new Mandalika circuit in Indonesia, Rea will be determined to slash Razgatlioglu’s advantage and put some pressure on the 24-year-old as the battle for the title reaches a critical point of the season.
Should the young Turkish challenger manage to increase his lead by a further seven points this weekend, Razgatlioglu would win the title even if he finished second behind Rea in the remaining races.
However, a confident Rea said: “I am expecting much more from Portimao. I think there’s a few factors that should work in our favour there. It’s a track where I’m quite strong as well; we expect to capitalise.
“We expect a good weekend. So that’s good – it’s good pressure. I like this feeling, I like the feeling when my back is against the wall – it’s nice. I like gritting my teeth.
“But I need a weapon to fight with: you can’t just grit your teeth and make it happen,” added the six-time champion.
“We need to fix the small issues we’re having in these hot conditions with the soft tyre. But, I think the soft tyre is on holiday now until next year. I think Portimao should suit us a little bit better than the previous rounds.”
Scott Redding claimed a third and runner-up finish on the Aruba.it Ducati at Jerez, where the Superpole race was dropped from the Sunday schedule after racing on Saturday was cancelled in the wake of the tragic death of 15-year-old Spanish prospect Dean Berta Vinales, who died following a crash in the first World Supersport 300 race.
Redding, though, is 69 points behind Razgatlioglu and last year’s championship runner-up would need an unlikely turn of events to move into contention.
Eugene Laverty, who returned to action last weekend after missing five rounds, is again set to replace Tom Sykes in the official BMW Motorrad team after the English rider was ruled out once more. Sykes suffered severe concussion in a crash in race two at Catalunya in Barcelona.
Free practice gets under way on Friday at Portimao, with Saturday’s opening race scheduled for 14:00 BST.
Meanwhile, the penultimate round of the British Superbike Showdown takes place this weekend at Donington Park, while Bishopscourt in Co Down hosts the final round of this year’s Ulster Superbike Championship.
Carrickfergus man Alastair Seeley wrapped up the Superbike and Supersport titles at the penultimate round two weeks ago as he returned to the domestic short circuit scene full-time for the first time since 2009.