In the space of just nine months in Manchester, Jesus had scored consistently, won effusive praise from Pep Guardiola and his emergence had even pushed Aguero into publicly questioning his own future.
At international level, Jesus was working towards the World Cup in Russia, where he hoped his performances for Brazil would justify the growing number of comparisons between him and O Fenômeno, the original Ronaldo.
“I'm always happy to hear things like that. People will always make comparisons and I'm happy with that one,” he told The Independent last December. “That's what I'm working towards.”
The year since, though, has not run quite so smoothly.
Jesus' failure to score at the World Cup despite starting each of Brazil's five games made him a natural fall-guy. The criticism of his performances and Tite's loyalty to him was loud and abundant.
Meanwhile, back in Manchester, Jesus appears to have lost the battle to be Guardiola's first-choice striker.
Now City's all-time leading scorer, Aguero has combined his natural predatory instincts with a willingness to work and press. As a result, he has started all of City's Premier League games this season.
By comparison, Jesus only has two league starts to his name and only one full complement of 90 minutes. In the Champions League, he was trusted against Lyon and Shakhtar Donetsk yet underwhelmed.
Whereas Aguero has clocked up 916 minutes under Guardiola this season, Jesus has only 558 to his name, with much of them coming during the closing stages of games already won. On Monday night at Wembley, he was introduced as a stoppage-time substitute.
The most telling and concerning statistic is that while Aguero has nine goals from this current campaign, Jesus has just two. The last of those came a month ago, away to third-tier Oxford United in the EFL Cup third round.
Is it any wonder that he was so keen to take the late penalty at Anfield last month, the one ultimately missed by Riyad Mahrez. “Obviously, I'm not happy,” Jesus admitted after the final whistle.
Is it any wonder, though, that Guardiola felt a striker who is yet to reach double figures for his club this calendar year was not the best option to take such a crucial spot-kick?
Though Jesus finished City’s title-winning season with a respectable record, it was a campaign split into two halves with bouts of scoring at the top and tail interrupted by an injury-hit, barren spell in the middle.
Rarely has Jesus looked the same player he did during his first few months in Manchester, when seven goals in 11 appearances in the second half of the 2016-17 campaign had Aguero worried he may be usurped.
Ever since, the scoring has been spasmodic, the finishing erratic and for a young striker with such obvious potential, there is a nagging sense that in those first few games he set too high a standard too early.
Jesus does not turn 22-years-old until April. Time is on his side in a way that it is not for Aguero, who is unlikely to retain his automatic starting place through the busy winter. It would not be a surprise to see Jesus back in form soon enough.
City return to the EFL Cup on Thursday, a month or so on from the win at Oxford, and he is likely to start. In Fulham, he will come up against a side beset by defensive issues, whose only clean sheet of the season came against Exeter City.
Though a low-key, Thursday night fixture which will not be televised may not seem of much importance, it provides Jesus with an ideal opportunity to return to scoring ways and start to emerge out of a testing time in his young career.
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