The Aston Martin driver spent much of the race playing the team game in building up a gap for Lance Stroll, which the Canadian could use to ditch his medium tyres and preserve his position.
Alonso's understanding was that this was for the final point and, when Stroll picked up a puncture after knocking his left-rear tyre from the rim on the entry to the Nouvelle Chicane, the Spaniard believed the responsibility was his to rescue a point from the race.
This prompted him to successfully defend from the chasing Daniel Ricciardo, despite being encumbered by worn medium tyres that he had been able to coax deep into the race, but was chastened when he found out he would not be rewarded for his efforts.
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"I got confused because when we [built the gap] and Lance was in front of me after the pitstops, they said, 'okay, we secured 10th.' We've been doing all this for that last point," Alonso explained.
"Then Lance had the puncture, I said, 'Oh, now I have all the responsibility in my shoulders with very old tyres to bring this point back home.'
"I was driving for 50 laps thinking that I was 10th.
"And then when I crossed the line and they told me P11, I said, 'Oh, so, uh, all that stress for nothing.' But anyway, it kept me alive.
"I don't know [why that happened]. When the red flag came out, Lance was P10, I was P12.
"And then at one point they reinstated Sainz in P3, so we were 12th and 14th, we should be 13th and 14th, but Lance was in front of Daniel - that he was not supposed to be.
"So I don't know in which position I started, and I don't know in which position I was driving."
Alonso reckoned that the nature of the race, which effectively cut pit strategy from its run-time owing to the early stoppage for the first-lap Kevin Magnussen-Sergio Perez incident, should once more bring up the debate over changing tyres under the red flag.
He felt that this denied the race "the only point of interest", and felt that going until the end on the medium compound - having started on hard tyres - was something of a risk that ultimately did not play out.
"When there is a red flag and then you change tyres and you go to the end, the only point of interest in a Monaco race is the pitstops that you have to do," Alonso reckoned.
"If you remove that excitement of a pit stop, then it becomes nothing.
"Maybe it reopens the conversations of when there is a red flag, not changing tyres or be obliged to have the same tyre or something, because if not, there are certain occasions that the race is compromised.
"In our case it was very unlucky again. I think we didn't have the pace.
"It was a bad weekend, no doubt about that. We cannot hide our performance, but also we cannot hide that we've been very unlucky.
"We started with a hard tyre just to go very end and have an alternative strategy.
"There is a red flag, so we have to fit the medium and do 78 laps with the medium, which is a kamikaze strategy, but it was the only way to try to score some points."
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