Regis Le Bris's men ran out 3-1 winners over the champions at the Parc des Princes last weekend, while Les Pirates' delayed clash with Nantes ended in a priceless 2-0 victory.
Match preview
Triggering the chain reaction of recent chaotic events within the PSG headquarters, Lorient travelled to the capital having failed to win any of their previous five Ligue 1 contests, but Le Bris's men taught the champions a footballing lesson last Sunday.
Goalkeeper Yvon Mvogo may have wanted the ground to swallow him whole when he inadvertently rolled the ball out to Kylian Mbappe for a tap-in - having wrongly thought that he was about to take a free kick - but his blushes were spared thanks to efforts from Enzo Le Fee, Darlin Yongwa and Bamba Dieng in a sensational Parc des Princes win.
Thanks to a first success since beating 19th-placed Troyes 2-0 in mid-March, Lorient have assured themselves of Ligue 1 safety with five games left to play and are clinging onto a top-half place, occupying 10th spot in the table with 48 points from their 33 matches thus far.
There may be some sense of disappointment around the Stade du Moustoir after Lorient threatened a European charge earlier in the campaign, but a top-10 finish is nothing to be scoffed at for Les Merlus, whose shooting boots have failed them at home more often than not recently.
Indeed, Le Bris's side have failed to score in four of their last six games in front of their own fans - including in each of their last two against Marseille and Toulouse - and Lorient will surely expect a basement-battling Brest side to put up more of a fight than the 10 men of PSG did.
Goalkeeping gaffes were not limited to the Parc des Princes last weekend, as after conceding five times to Toulouse in the Coupe de France final, Nantes number Alban Lafont's horror show continued at the Stade Francis Le-Ble.
In a crucial relegation showdown between Nantes and Brest, Lafont swiped at thin air when trying to clear the ball - allowing Jeremy Le Douaron to tap home into an empty net - before a Mathias Pereira Lage header sealed the deal for a rejuvenated Pirates outfit.
Developing a sense of resilience at the perfect time, Eric Roy's side made it six games unbeaten with their triumph over Nantes and have surged out of the relegation zone into 14th place in the process, now three points clear of Les Canaris in the final demotion spot.
Another shut-out against Nantes made it three clean sheets in a row for Brest, who also travel to the Stade du Moustoir on a four-game unbeaten run away from home, although their last three on the road against Troyes, Reims and Ajaccio have all ended level.
However, three of Brest's last four meetings with Lorient have ended in defeat - including a 2-1 beating at the Stade Francis Le-Ble earlier this season - but their trip to the Stade du Moustoir in the 2021-22 campaign ended in victory by the same scoreline, where current Merlus attacker Romain Faivre was on the scoresheet for Les Pirates.
Lorient Ligue 1 form:
D
L
D
L
L
W
Brest Ligue 1 form:
D
W
D
W
D
W
Team News
Lorient have been dealt a couple of fresh defensive blows ahead of the visit of Brest, as centre-back Bamo Meite must serve a suspension for an accumulation of yellow cards, while right-back Gedeon Kalulu came off on the 65-minute mark with an unspecified injury.
However, Kalulu is understood to have trained as normal this week and could force his way into the squad alongside Theo Le Bris (groin) and Julien Laporte (knee), while Jean-Victor Makengo also has a slim chance of a comeback.
Igor Silva (thigh) and Vito Mannone (foot) are not expected back in time for Sunday's game, where Kalulu could deputise in central defence for Meite as Stephane Diarra and Yoann Cathline battle for a start on the right.
As for Brest, Roy managed to engineer a precious win over Nantes without the services of key attacker Franck Honorat, who is nursing an Achilles problem and is uncertain for this weekend's derby too.
Romain Del Castillo was able to come off the bench in midweek, although Roy has admitted that the 27-year-old is yet to fully recover from a knock to the ankle, while right-back Noah Fadiga is also confined to the infirmary.
Even if Del Castillo's ankle swelling goes down in time for the weekend, Pereira Lage has surely done enough to hold his position in an unchanged XI.
Lorient possible starting lineup:
Mvogo; Kalulu, Talbi, Le Goff; Diarra, Innocent, Abergel, Yongwa; Faivre, Le Fee; Dieng
Brest possible starting lineup:
Bizot; Lala, Chardonnet, Brassier, Duverne; Belkebla, Lees-Melou, Camara; Pereira Lage, Mounie, Le Douaron
We say: Lorient 1-1 Brest
There is much less on the line for Lorient than Brest at this stage of the season, but Le Bris will not want to witness any drop-off in performance following last week's memorable success, which should lead to a combative and closely-fought derby this weekend.