Chelsea's end-of-season form cost them the Premier League title. From mid-March they lost to Aston Villa, Crystal Palace, Sunderland and drew with Norwich City - and, in their last seven matches, their so-called star No. 10 failed to score a single goal or provide a single assist. Oscar, it is clear, must do much better next season in order to stay at Stamford Bridge.
The main reason Jose Mourinho agreed for Juan Mata to join Manchester United in January was because of the Brazil international, who performed well in the first half of the season. However, from New Years Day until May 11 - the final day of the 2013/14 season - Oscar scored just two Premier League goals, both against a 10-man Arsenal side who were dead on their feet at Stamford Bridge, and provided one solitary assist in a 4-0 win over Tottenham.
These statistics, even for a 22-year-old, are desperately poor. We're not talking about a boy of 18 here - this is a Brazil international with 29 caps and over 100 appearances for Chelsea under his belt.
Whisper it quietly, then: Oscar failed to perform when Chelsea needed him most this season. Compare his performances with those of Yaya Toure, who typically plays in a deeper role than Oscar for Manchester City, and the differences are stark.
The Ivory Coast international, from New Years Day, scored 10 Premier League goals and provided six assists. Quite simply, there is no comparison between the two players. Two players who were expected to play pivotal roles for their clubs in the final weeks of the campaign. Only one of them stepped up to the plate - and the brilliant Toure was the driving force behind City's successful title challenge.
It could be argued that Oscar's goals and assists stats would look healthier if Chelsea had a world-class forward leading their line. But this would be a flimsy excuse: the South American still had world-class talent around him, and Mourinho even resorted to dropping him from his starting eleven altogether on occasions during the final weeks of the campaign.
Oscar's performances had dipped so dramatically that Mourinho benched him for the matches against Stoke City and Swansea City, while he was left out of the Blues' squad altogether for the trip to Anfield. He was left on the bench for the crucial Champions League clash against Atletico Madrid three days later, while a hip injury apparently kept him out of the 0-0 stalemate against Norwich City.
Nobody is doubting Oscar's quality. We've all seen enough over these past two years to know he is a very special talent indeed, but just because he's an exciting talent doesn't mean he should be immune from criticism. And, the fact of the matter is, very few people have picked Oscar out as under-performing in the final weeks of the 2013/14 campaign.
Mourinho, a famously demanding coach, will expect more from his key playmaker next season. A repeat performance could even leave question marks over his future as a Chelsea player.
Hopefully it won't come to that - but Chelsea supporters, and their notoriously demanding owner, expect success. In order for that to happen, the team's No. 10 needs to produce the numbers - better numbers - every season.