Bo Svensson had nothing to do with Aarón Martin in his first six months as coach of FSV Mainz 05.

The left-back was on loan at Celta Vigo in the Primera División in the second half of last season, and his return in the summer was considered more of a pro forma act.

“At the beginning of the preparation I didn't believe that he would become a permanent fixture,” says Svensson - and anyone who had seen the Spaniard, who had been at Bruchweg since summer 2018, in his second and third Mainz seasons, could probably imagine it even less.

When, after a strong first Bundesliga year, the hoped-for lucrative offers from big clubs failed to materialize, Aarón looked listless. Instead of working on reducing his defensive deficits, he adapted the previously strong offensive performance to defensive work, and from the second half of 2019/20 onwards he mostly found himself on the bench. The trip to Vigo a year later seemed just the lead-up to a permanent transfer.

"He wasn't sure if he wanted to stay," says Svensson, "and we weren't sure if he was the right man for us." Had a reasonable financial offer been received in Mainz, the coach would have had such doubts no longer have to deal with.

But those responsible for the Celta were apparently playing for time, wrongly assuming that they would get Aarón, who had moved from Espanyol Barcelona to Mainz for nine million euros, for a small fee.

Good conversations and achievements

Then an unexpected second metamorphosis of the now 24-year-old set in.

The “good impression” from the discussions that Svensson reports carried over to the performance.

Anderson Lucoqui, the newcomer from Bielefeld, was initially number one in this position, "but when Aarón was challenged, he delivered," says Svensson.

Substitute in the 80th minute in the cup game at SV Elversberg - which still meant 40 minutes of play plus successful participation in the penalty shoot-out that had been won - there was no sign of the old phlegm.

In the first two games of the season, the U-21 European champion from 2019 was part of the starting line-up because Lucoqui was one of the numerous Mainz residents in corona quarantine.

Then Aarón took a seat on the bench again, absent from time to time due to groin problems.

But since the second half of the game in Dortmund he has overtaken his internal competitor for the time being.

Speaking of which: Svensson is very impressed by the Spaniard's running quota.

"He didn't even come close to as many meters as last against Gladbach in all of his previous 05," he says: "That already shows a development."

Aarón is not yet the perfect defender.

"He still has his construction sites, when the ball is on the right-hand side, he forgets to move in," Svensson gives an example.

But he sees that "our way of playing football gets under his skin".

Aarón has a lot more potential, and he knows it too.