"But I have been here since the early 70s," the Italian said recently, "and I know that risk is something you have to live with in formula one."
Ecclestone, F1's chief executive, usually likes to see the sport's top drivers spread across the most competitive teams.
But he thinks Alonso versus Raikkonen at Ferrari, F1's most famous team, will be "fun".
"I thought Ferrari would win the title in 2013," the 83-year-old Briton told Italy's La Gazzetta dello Sport, "and I cannot explain why they were not competitive.
"Alonso, in any case, drove well," he added.
Ecclestone answered "yes" when asked if the Spaniard was right to criticise the Maranello based team mid-season.
But that criticism earned him a rebuke, and many believe Ferrari's decision to replace Alonso's preferred teammate Felipe Massa with Finn Raikkonen for 2014 was part of a shift away from the Spaniard.
"Now the dust has settled," Ecclestone explained, "and we will see a different Ferrari in 2014.
"Alonso-Raikkonen is a classic combination that Enzo Ferrari would have liked to see. It will be fun with those two.
"If Kimi drives as he did many times in 2013, it will stimulate Alonso, but what Ferrari really needs is a good car. Otherwise there is nothing to talk about," he added.
Ecclestone has said the team with the best all-new V6 engine will win the 2014 title, but he also thinks "luck" will play a big role.
"There is no guarantee that the best driver will win the title," he insisted. "The title will be for the luckiest one. At the moment I have no favourite."