Renault Sport's Formula One head honcho has issued a clear warning to the young Brit as the season nears it's midway point. Jolyon Palmer has not had the best start to his 2017 Formula One season. Actually, that's being too generous. Jolyon Palmer has had an absolutely disastrous start to his 2017 Formula One season. A spate of rookie-mistakes from a non-rookie, clumsy collisions, being thoroughly out-classed by his teammate and most crucially; scoring zero points thus far, has meant that Jolyon has rather placed himself on the chopping block in the unforgiving world of F1. This week has seen the most serious threat to his drive yet, as none other than the Renault F1 team principle, Cryril Abiteboul, come out and straight up admit that Jolyon must start delivering from here on out, or else they'll have no hesitation in replacing him. I'm paraphrasing there, but behind all the media-jargon and spin, that's essentially the crux of what he said. "F1 is not an environment where anyone can say loudly, 'I'm safe'. To a certain degree there are two questions. There is Jo, and there is a second driver. Right now my focus is on Jo. Jo has to deliver. What would happen then, I don't want to elaborate on that, and even further, who would be stepping in, because that's absolutely not the point for today. "The fact is that Jo has a car which is a point-scoring car, and he has to enter into the points. Full stop." This is as clear an indication that a driver lineup change may well be on the cards when F1 returns to action in Belgium. Enter Robert Kubica. The Polish driver who last drove for Renault F1 back in 2010 when they were formerly known as Lotus. No no, the other Lotus... Lotus Enstone. Confused? Don't worry, welcome to F1. Anyway, earlier this week, Renault offered Kubica the chance to test the 2013 Lotus at the Valencia circuit to see how he would cope in the tight confines of a Formula One car after his horrific injuries sustained while rallying before the start of the 2011 F1 season. He's lucky to be alive, let alone drive a Formula One car. Many believed he many never set foot in an open wheeler again. But some six years later, here we are. The test he conducted was deemed a success as Renault were very impressed with his speed. He'll obviously be a little rough around the edges, which is to be expected, especially after being away from the circus for so long, but to cover an entire Grand Prix weekend's distance in one day of running is incredibly impressive. Prior to his accident, Robert was one of the up and coming stars of F1. Having given Sauber their first and only win in 2008, Robert's speed and car control was up there with the likes of Alonso, Hamilton and Vettel. Many paddock insiders believed he may have been better than the lot of them, he just needed the car under him to achieve it. But unfortunately it wasn't to be. So here we are. An unimpressive and under-delivering Palmer threatened with the axe, Robert Kubica gets back in an F1 car and Renault start saying lots of warm and fuzzy things about him. If Jolyon can't save his sinking ship fast, which let's be honest, is highly unlikely as he's taken on too much water already, could we see the return of Robert Kubica in time for the Belgian Grand Prix? And if not Robert, then who? Alonso has been seen talking with Renault personnel recently and rumours of a 2018 drive are looking likely, but he's almost certainly going to be blocked by McLaren when it comes to a mid-season move. There's also Esteban Gutierrez, who has said he will continue to try to make his F1 career work, but after several years of trying, he resembles a Mexican version of Palmer more than anything else. Renault have a problem. They need results, and Palmer isn't giving them that. The driver market is looking somewhat thin at the moment as the good ones are either already tied into contracts, or they're simply not interested in getting involved in the Renault F1 project. Who would you take? Let us know in the comments.