Spengler: Radio problem cost me win

The Canadian had led the opening stint of the race after starting from pole position in his HWA Mercedes.

But, after Rockenfeller dived in for fuel and tyres as soon as the mandatory pitstop opened on lap 11, Spengler was left out on older rubber for two laps before he was able to make his first planned stop.

Spengler said that he had missed a call to pit on lap 12, and that the moment had robbed him of a chance to add to his win at the Hockenheim season-opener.

"I had a problem with the radio communication. I didn't hear it," he said. "I just got a very short call before the pit entry and it was a bit too late to come in.

"That probably cost us first place, which is a shame. And I'm pretty disappointed."

Mercedes motorsport vice-president Norbert Haug doubted, however, that Spengler could have kept Rockenfeller's Abt Audi behind him for the rest of the race, even if he had not suffered from radio problems.

"The gap he [Spengler] has at that stage was big enough that he would have kept the lead if he'd pitted as planned," Haug said. "But I have no idea if he could have kept it to the finish. Probably not.

"Generally the speed was not so good in the last sectors of the races. The qualifying speed has been very good, but the race speed [for all Mercedes cars] is not quite there, even if it is only a few tenths [missing]."

Spengler's runner-up spot means that he increased his championship lead to eight points over Rockenfeller and Martin Tomczyk, who finished third at Zandvoort.