The men and women picked to run the EU for the next five years face a grilling by the European  Parliament this week which could claim the scalp of at least one of them.
France's Pierre Moscovici, the incoming economic affairs commissioner, Britain's Jonathan Hill, named as financial services boss, and Miguel Arias Canete, the Spaniard chosen as energy and climate change czar, are the most likely to be caught in the crosshairs.
The European commissioners will be quizzed on subjects ranging from the flatlining economy to the Ukraine crisis by a parliament increasingly keen to flex its muscles.
The interviews of all 27 commissioners picked by former Luxembourg prime minister Jean-Claude Juncker start on Monday and will finish on October 7, with each session expected to last around three gruelling televised hours .
The EU lawmakers can ask for a commissioner to be dropped or to have their portfolio changed, something they did in both 2004 and 2009.
The European Parliament will also approve or reject the new Juncker commission line-up as a whole in a vote on October 22.
- Stalling economy to test  Moscovici -
Juncker's new team will oversee policy for a group of 28 countries with a total population of more than 500 million, making the bloc the largest economy in the world, but one facing huge challenges.
Beset by high youth unemployment and the risk of deflation, Europe's stalling economy risks falling into the doldrums for the next 10 years. On its borders, meanwhile, the EU faces challenges including a resurgent Russia and Islamic militancy.
Moscovici, a former French finance minister, will be a prime target for lawmakers when he appears on Thursday after he was named to the post despite German reservations about Paris's ability to meet Brussels budget rules.
"As a minister he did nothing, he let the deficit run. He knows the EU, he is competent, but not for this post," said conservative German Euro MP Herbert Reul.
Hill faces a far rougher ride in his interview on Wednesday than he is used to in his old job as the leader of Britain's House of Lords.
Hill's job appeared to be an olive branch to Britain, which is set to hold a referendum in 2017 on its EU membership, but lawmakers said it was "absolutely incomprehensible" when London is so set against regulating its huge financial services industry.
French euro-MP Alain Lamassoure said Moscovici and Hill "are going to suffer."
- Juncker rises to challenge -
But Juncker -- a wily political who was approved by the EU parliament as European Commission president in July -- appears to have taken a perverse pleasure in both appointments.
"It seems to me that those who best understand the problems of certain countries come from those countries themselves," Juncker said when he unveiled the line-up earlier this month.
Spain's Canete is perhaps the most controversial nominee for his job as energy and climate commissioner -- a hot post given the Russian threat to Europe's gas supplies over the Ukraine crisis.
He has already been forced to sell his shares in oil firms but faces criticism over continuing family links to the energy industry, especially from the Greens in the European Parliament.
Lawmakers are also likely to quiz him on Wednesday over allegedly sexist comments about a political rival.
Hungary's Tibor Navracsics faces tough questions over his closeness to Prime Minister Viktor Orban, whose relations with the EU are strained because of a crackdown on civil liberties and his ties to Russian President Vladimir Putin.
Slovenia's Alenka Bratusek is also controversial due to the way she apparently nominated herself as commissioner just before quitting as prime minister.
Ireland's Phil Hogan, widely seen as a shoo-in, could now face problems over a legal row with an Irish legislator.