Luiz Razia's December claim that there may be more changes to the Marussia F1 line-up appear to have been based on more than hope after Timo Glock admitted that his position in the line-up became precarious after the Brazilian Grand Prix.

The German, who has already confirmed that he will switch to the DTM touring car series with BMW in 2013, revealed that Vitaly Petrov's pass on Charles Pic late in last season's F1 finale was a major blow to his hopes of remaining a part of the team he had devoted three years of his career to. Petrov's successful move on the second Marussia secured not only eleventh place on the road, but also tenth overall in the constructors' standings, and the prize money that went with it. Prior to that, Glock's twelfth-place finish in Singapore had been the trump card, with Caterham unable to post anything better than a series of 13ths.

"After the last race in Brazil, I felt sick because we had really been counting on being able to keep the tenth place," Glock told Germany's speed-academy website, "It looked good for a long time, as I was also in the running close to the top ten before the safety car came out. My former team-mate still had it in his grasp but, for whatever reason, he could not keep it, and that was the point where I began to be concerned about the situation."

With Pic moving to Caterham over the winter, the seat alongside Glock was taken by erstwhile Marussia reserve Max Chilton, but the Briton's appointment elicited surprise from Razia, who had believed that his own talks with the team were moving in the right direction. Commenting on his disappointment, however, the Brazilian suggested that the line-up was far from final, prompting question marks to be raised over Glock's position.

"The team came up to me and openly described the situation," the German continued, "Eventually, we sat down together and went through are certain possibilities. I then realised that the economic situation was difficult for the team, and that it would be difficult to make the expected step forward. Marussia now has a good base and I believe that the new car will be a step forward, but I also know what it takes to make the big step, and that is why I've been thinking about my future."

Underlining the amicable nature of the split, Glock said that he wished Marussia well for 2013.

"I'm sick because I put so much heart and soul into it, but I hope the team moves forward," he admitted, "I know that it would be much worse off [financially] if I had stayed there. There are many people who have invested endless effort, day and night, to make this team work, so I cross my fingers and hope that things gets better. I can only watch on TV now, but I'll do so with satisfaction when they take a step forward."

Unsurprisingly, Glock does not rule out a possible return to the top flight in future, although he insists that his focus now is on chasing the DTM title with current champion BMW.

"I'm always open [to offers] but, at the moment, I am concentrating fully on the BMW commitment and not thinking about what might happen in 2014 or 2015," he claimed, "The last few weeks were very intense, with the separation, the [Valencia DTM] test and [signing] the contract with BMW, and, in that time, I have not had any thoughts [about F1]."