Pumas celebrate a goal against Necaxa. ALFREDO ESTRELLA/AFP/Getty Images

The second week of matches in the Liga MX's 2018 Apertura is in the bag, with four teams on six points -- Pumas, Cruz Azul, Monterrey and Tigres. But four -- Chivas, Pachuca, Leon and Veracruz -- are still to get off the mark.

Here's what we learned:

Castillo who? Pumas edge thriller against Necaxa

The sale of Nico Castillo to Benfica was supposed to be a significant blow to Pumas' chances this Apertura. But the Chilean striker was a distant memory as Pumas recorded a 5-3 win over Necaxa on Sunday, with two goals from Castillo's replacement Carlos Gonzalez.

This was an end-to-end game that will live long in memory and one that showed Pumas may have covered for Castillo's departure better than previously believed. Pumas had been down twice at 1-0 and 2-1, but managed to show grit to overcome a spirited Necaxa.

In truth, Pumas created chances almost at will, racking up 12 shots from inside the box against a Necaxa side that went to Estadio Olimpico Universitario with the intention to go out and attack from the first whistle.

Alan Mendoza and Alan Moza -- two promising young Mexican full-backs -- both netted goals for Pumas. Moza's goal was particularly impressive.

For Necaxa, 20-year-old Chilean Victor Davila scored twice to make it three for the season. The forward is an outstanding young talent and Marcelo Michel Leano's Necaxa is looking good going forward, but it will have to improve at the back if it is to push for the playoffs. That was highlighted by an embarrassing mix up between Ventura Alvarado and Hugo Gonzalez for Gonzalez's equalizer against his former club in the 54th minute.

This wasn't one for the defensive purists, but was a lot of fun.

Chivas struggle as Cruz Azul march on

Torrential rain fell ahead of Chivas' home opener and the difficult times for the Guadalajara club continued with a 1-0 loss to Cruz Azul on Saturday evening.

The conditions and water-logged pitch were always going to make this an atypical match, but with a healthy attendance behind a Chivas side looking to turn the page on a torrid last 12 months at home, this was a game that could have provided a boost.

Instead, a Martin Cauteruccio solo effort in the 47th handed Cruz Azul the points.

Chivas veteran Carlos Salcido struggled in central midfield, while Eduardo "Chofis" Lopez and Hedgardo Marin weren't convincing.

Chivas coach Jose Cardozo complained about the state of the pitch afterwards and had a point, but he should be concerned that after only two games of the season Chivas CEO Jose Luis Higuera and VP Amaury Vergara have already felt the need to come out and back him.

For Cruz Azul coach Pedro Caixinha, this has been a confidence-boosting start to the Apertura, while Cardozo and Chivas are already desperate for a result next weekend away at Toluca -- one of the toughest games in Liga MX.

Ferretti to El Tri rumors swirl but attention on Tigres

Ferretti is reportedly the top target for Mexico. Hector Vivas/Getty Images

A report ahead of Tigres' 1-0 win on Sunday over Club Tijuana suggested that Ricardo "Tuca" Ferretti is the No. 1 candidate for the Mexico national team job, despite the Brazilian having repeated he isn't interested in leaving Tigres.

Ferretti was certainly animated during the game. Despite the victory, Ferretti was lamenting the position of a photographer near to where Lucas Zelarayan was taking corners and screaming at his players late on as they almost let a game that they had dominated slip.

Ferretti's team has now gone 29 games without a loss at home and, while Tigres tend to give the opposition a chance by not finishing off games, they are once again primed for a title push.

Given the fact Ferretti has a contract with Tigres until 2020 and that he has just witnessed Juan Carlos Osorio go through a roller-coaster of criticism, (including intrusive stories about his personal life while in the role of Mexico manager), it's unlikely the veteran will be tempted, even if he may be the top target.

Lobos BUAP against Veracruz a bad example for Liga MX

There's been a lot of talk about Liga MX's pro/rel situation and some poor communication from the league in explaining clearly what its future vision is and whether the aim is to get the league up to 20 teams.

But Lobos BUAP against Veracruz on Sunday gave an insight into what it is not. The wolf howl from the PA that echoed around Estadio Universitario BUAP seemingly every other minute only served to highlight just how few people were in attendance. Let's not forget that Lobos BUAP were actually "relegated" last season, but they were able to pay their way back into Liga MX because second division champion Cafetaleros de Tapachula didn't fulfil Liga MX entry requirements.

This should have been an important game in the context of the relegation battle for next May, but the match lacked any real appeal for the neutral, or even the supporters of the two clubs, with only 5,845 inside the stadium.

Not that anything should be taken away from Lobos BUAP or coach Francisco Palencia. The home side earned a deserved 2-0 win and might well achieve one or two surprise results this season.

Veracruz and its haphazard squad building looks set for another relegation fight.

Strugglers and winners from first two weeks

It's obviously too early to be making sweeping claims about how this Apertura will turn out, but there will be concerns at the teams yet to win a single point.

Pachuca last reached the playoffs in the 2016 Apertura and have started this season with two losses, without even netting a goal. Incoming coach Pako Ayestaran hasn't been able to significantly strengthen a squad that were shorn of Keisuke Honda in the offseason. It's not time for the alarms to sound, but Pachuca's plight is slightly worrisome.

Leon are in exactly the same position as sister club Pachuca, having lost 2-0 at home to Monterrey on Sunday after Pedro Aquino was sent off in the first half.

Veracruz weren't really expected to do well, while Chivas are in the same boat as Pachuca in terms of expectations.

At the other end, Pumas and Cruz Azul are perfect, as are Tigres and Monterrey.