It wasn't the absence of the promised pre-match lap of honour to show off the sparkling Libertadores Cup trophy. It wasn't the home side sporting an unfamiliar golden strip - a custom in Argentina whereby the hosts change shirts if there is a clash in team colours. It wasn't even the sight of the ludicrously scantily-clad cheerleaders braving the arctic winds in the build up to the match. It was all to do with one man who was nowhere to be seen. Juan Roman Riquelme.
Boca are expected, and expecting, to see the next six months reap three more trophies and confirm their status as heavyweights in world football. Victories in the domestic league competition and the Copa Sudamericana are anticipated before December's duel with Milan in Tokyo for the Intercontinental Cup. Travel agencies in Buenos Aires are already enjoying healthy profits on their $5,000 all-inclusive packages to fly to Japan for the game against the rossoneri. Those travelling are confident that they will witness Boca being crowned club champions of the world.
Elevated hopes are underpinned by Boca's victory in this years Libertadores cup. The xeneixes displayed irrepressible form in Latin America's premiere tournament, as they steamrolled there way to a fourth Libertadores trophy in just seven years.
If Boca are to build on that victory, however, and cement their position as the giant of South American (and indeed world) football, it hinges on one man ? Riquelme. And the issue isn't about the playmaker finding his form, it is more to do with him finding his way to Buenos Aires.
Riquelme spent the last six months on-loan at Boca after exasperating Villarreal directors beyond redemption. His increasingly regular whims in Spain included missing training sessions at will, jetting back to Argentina without obtaining permission from the club and insisting he deserved longer holidays. Villarreal are no Real Madrid or Barcelona - they only debuted in Spanish top flight as recently as 1998. Superstar behaviour could not be tolerated as relegation threatened the modest club half way through the season. Riquelme was shipped off to Buenos Aires in February.
Back at his spiritual home, the Bombonera, playing for club and country under coaches who indulged him with tactical liberty and back in Argentina close to his family, Riquelme produced some outstanding football. He single-handedly won the Libertadores Cup for Boca with eight goals in the competition. In the Copa America he nearly guided Argentina to their first title in 14 years, only for a debacle in the final against Brazil to steal the limelight from him. Yet his future has yet to be decided.
Rumours circulating imply that an extension of the loan deal is a formality. Yet top brass at Boca are keen to play down those suggestions. "It would be music to our ears if that was the case" insisted Boca vice-president Pedro Pompilio to reporters, saying that the move depends entirely on Villarreal. Nonetheless, it is expected that Riquelme will be soon be wearing the blue and yellow of Boca again. And how they need him.
"There is no Plan B," admitted coach Miguel Angel Russo, who has kept the number 10 shirt under lock and key as he waits for Riquelme to arrive. "There is nobody who can replace him, and there is nobody who can reproduce the form he showed in the first half of this year with us," concluded Russo after an uninspired draw against Rosario Central.
"If we had won this game," continued the coach, "one of every four questions would be about Roman. If we drew, as we did, four out of every five questions would be about him." And that is exactly what happened.
Boca failed to score against Rosario Central. It may have been the first match of the season, and the players may have been tired after an exhausting tour of the US (devised to raise the funds necessary to pay Riquelme's $4.5m wages). Yet the pressure is intense at Boca, and silverware is the only way to ease the atmosphere. Many agree that the arrival of Riquelme is vital for success. "Let's not kid ourselves," said right-back Hugo Ibarra after the 0-0 against Central, "of course you miss a player like Roman." Midfielder Sebastian Battaglia agreed and added "the team is unbalanced, but we have to get on with it and win games."
Whispers in Buenos Aires hint that Juan Roman Riquelme is only returning to Spain next week to pick up his limited edition Mini Cooper and turn his back on Villarreal for another six months. Boca will be hoping that Riquelme's mini loan adventure continues for the rest of the year, because right now it is evident to see. With no Roman, there will be empire for Boca.