The Mercedes AMG Petronas F1 team's "no sidepod" W13 was the talk of the paddock on Day 1 of the Bahrain pre-season test on Thursday. The Brackley-based team unveiled their radical design ahead of testing, and it immediately got the attention every team and driver on the grid.

Red Bull Racing got the comments rolling with Christian Horner expected to have questioned the legality of the Mercedes to a German publication. The Austrian team denied making any official comment about their main title rivals.

Ferrari team principal Mattia Binotto, meanwhile, was full of praise for the Silver Arrows team calling the "no sidepod" design a great concept. The Italian was also certain that Mercedes were not doing anything illegal, as they would have consulted the FIA every step of the way before finalising such an aggressive design.

Red Bull and Ferrari, however, did have one issue with the new Mercedes and it was not the sidepods. Both teams questioned the legality of the rearview mirrors, with Horner suggesting that they were not "mirror mounts" but wings that were housing the rearview mirror.

Christian Horner
Red Bull team principal Christian Horner ANDREJ ISAKOVIC/AFP

"Those are not mirror mounts, but two wings. In addition, they have built vertical baffles on top. They have nothing to do with the mirror mount," Horner said, as quoted on BBC Sport.

Binotto also questioned Mercedes' rearview mirror design, stating that teams were always told that they should be part of the car's aerodynamics. He feels the regulations needs to be clear, because it could trigger teams to start designing mirrors that look like "spaceships".

"No doubt it is a great car - that should not be a surprise to us," Binotto said. "A concept quite different to ours, quite interesting with the cooling layout, and the sidepods."

"On the mirrors, it was surprising - we were not expecting that. We always said the mirror should have no aero[dynamic] purpose and the way they treated their cars there is a significant aero purpose in the mirrors."

"The risk in the future is that all teams will start designing mirrors that look like spaceships. In the spirit of what we intend to do for the future, it is something we need to discuss," he added.

Mercedes team principal Toto Wolff, on the other hand, was not concerned about any problem developing with regards to the rules. The Austrian confirmed that the FIA had been kept in the loop during the entire process - despite Ross Brawn labelling the Mercedes design as "extreme interpretation of the rules".

Toto Wolff
Toto Wolff is hoping for a clean title fight next weekend ANDREJ ISAKOVIC/POOL via AFP