Relief is surely the dominant emotion in the Argentina camp this morning. Here's Sam Kelly's latest report from the Copa América.

'A new Copa has started', Lionel Messi told the press after Monday night's 3-0 win for Argentina against Costa Rica. Messi wasn't in a press conference, or a mixed zone; he was picking up his man-of-the-match award. Normally he'd just stand for a couple of photos and leave with the gong, to answer questions outside, but he grabbed a microphone to thank 'the people of Córdoba for how they've treated all of us, especially myself.'

Argentina had finally looked like a team, scored some goals, and got their first win of the tournament, and whilst the vanquished opponents might only have been Costa Rica's Olympic side (Costa Rica and Mexico, having fielded their first teams during the Gold Cup last month, have sent representative sides to the Copa América), no-one in Argentina minds too much just at the moment. The important thing, after all, is that the side are in the quarter-finals after Sergio Batista, the manager, finally saw the light and realised his previous system just wasn't working.

Batista deserves some credit for the changes, but his past record still stops one from showering him with praise. Few think this is likely to be a road to Damascus moment for him. More likely, now he's won a game with this system (which previously suggested would be a 4-2-1-3, but in practice was more of a 4-2-3-1, for all the difference that makes), he'll stick to it in the knockout stages whether or not it's the one that looks best for the opponents he faces.

The key change from the previous 4-3-3, with Messi in the 'false nine' role, was putting Gonzalo Higuaín just in front of him to play as a proper number nine. Higuaín didn't have his best game, missing a few chances, but that didn't ultimately matter. What he did do was force the centre backs to concentrate on him, thus freeing up the space which allowed Messi to roam to better effect than he had in the previous two matches, when he'd had to drop frustratingly deep to get the ball, thus diminishing the impact of his passing.

Messi hadn't been bad in either of those matches; he'd done everything right that his team-mates' play and the system his manager had given them allowed him to. But on Monday he was superb. He didn't manage to score himself, but no-one is begruding him his gong for best player of the match, after two wonderful second half assists, first for Sergio Agüero's second, and then for Ángel Di María's goal to put Argentina 3-0 up.

The real test is yet to come, without knockout opponents set to be decided on Tuesday when Group C concludes – Uruguay or Chile look the most likely opponents in Santa Fe on Saturday, but Peru (who play Chile) are currently in second spot prior to those final two group games, and even Mexico could yet qualify if they manage to shock Uruguay on Tuesday night in La Plata.

Argentines will now be hoping the pressure has lifted from the national team, and if nothing else it seems that the mistake made in previous Copas of peaking too soon might be avoided – unless Monday night was the peak, of course. The crowd in Córdoba were highly supportive of the team throughout the match, and the players will be hoping that mood infects the fans back in Santa Fe for the quarter-final; Argentina were roundly booed during their 0-0 draw with Colombia there a few days ago.

One player who'll almost certainly be wishing he could play all his matches in Córdoba must be Javier Pastore. The Córdoba native was cheered and heard his name chanted throughout, and finally got some playing time – his first in the Copa – when he came on for Higuaín with eleven minutes to go. Given the highly impressive performances of Agüero and Di María alongside Messi, it's hard to see where Pastore would fit into the starting XI for Batista, but many will be glad for the confirmation that he's not been forgotten about. Pastore's the kind of player who could still prove a very useful game-changer for Argentina in this campaign.

Colombia, of course, are the group winners, and almost seem to have benefited from the pressure heaped on the hosts in the same group. Their 2-0 win over Bolivia was a polished performance, and with Radamel Falcao García getting both goals – the second from the penalty spot – by the midway point of the second half, they were able to ease up without ever looking in danger of letting Bolivia back into the match. They'll await the runners-up in Group B, who might just end up being Brazil.

Group B is, improbably, topped by Venezuela, who battled to a 0-0 draw with Brazil in their first match and then beat Ecuador 1-0 in their second. If they beat Paraguay in Salta on Wednesday, they'll win the group regardless of Brazil's result over a lacklustre Ecuador. Paraguay will be a seriously tough challenge for Venezuela so many will be looking to see whether the excellent performance against Brazil was just a case of being hyped-up and well-prepared for their big name opponents. Venezuela do now have their quarter-final place guaranteed though (they can't finish below third in their group, and they already have more points than Costa Rica, third in Group A. This means Venezuela would be at least the second-best of the three third-placed sides, and as such would go through even with a loss), so the lack of pressure might make them even more dangerous for Paraguay.

On Tuesday, Chile ought to beat Peru with something to spare, and Uruguay v Mexico in La Plata is a game I'm looking forward to attending. Uruguay's start against Peru was a stuttering one, their match against Chile (a 1-1 draw) much more entertaining. As the Copa moves on, it'll be interesting to see if any of the other candidates can breathe life into the campaigns in the same way as Lionel Messi's Argentina have done.

Sam is a freelance writer based in Buenos Aires, and a regular contributor to the likes of IBWM, Soccernet, and When Saturday Comes. He's the brains behind Hasta El Gol Siempre and the Hand of Pod podcast, both of which are the outstanding online resources for all things Argieball. Follow him on Twitter @HEGS_com.