The two-time world champion caused a shock when he announced he would miss the jewel in the crown of the F1 calendar to make his debut in the Indy 500, especially because Monaco is likely to be one of McLaren's strongest races due to the lack of reliance on engine power on the twisty street circuit.
Alonso acknowledged that Monaco could be a high point for McLaren this season, but he said that was not enough to deter him from missing the race.
"Monaco definitely is the race that I was preparing all season for because with our package we should definitely be competitive there," Alonso said.
"This clash with the Indy 500 is bad news in that aspect but overall I have much more to win than to lose.
"In Monaco, even if you are in the top five or top three or whatever it's OK, it's an enjoyable result.
"But the big possibility to win a legendary race is much greater than any position in Monaco.
"It's not that I'm not racing in Monaco, the biggest news is that I'm racing the Indy 500 and it's something that's attractive.
"It's a unique day for motorsport, where McLaren-Honda is racing in Monaco and Indianapolis on the same day."
Read the full article on eurosport.co.uk: Alonso: Indy chance 'much greater' than Monaco