The reaction among partners to today's news that DLA Piper senior partner and global co-chair Juan Picon has resigned to join Latham & Watkins has generally been one of shock.

"Bloody hell," one former partner says on hearing of Picon's move, while another exclaims: "Goodness me!"

The general consensus is that Picon's exit, just 18 months after taking up the senior partner post at the firm, is a heavy blow for DLA Piper, particularly as it comes during the tricky transition phase following the retirement of longstanding leader Sir Nigel Knowles last year.

There have been whispers of management-related tensions in the firm's Noble Street headquarters for some time, and the loss of Picon – who is joining Latham & Watkins as Madrid office head – ushers in more uncertainty .

"I am surprised – it is a big defection," one ex-partner says. "It will be a loss to DLA because he is very talented and has a very strong client following."

Another adds: "He was always a big name in the market and for the firm; not just as a leader but also as a practitioner in the Spanish corporate market. It is doubly significant in what it says about the leadership of the firm, but also what it means vis-a-vis clients who are keen on having a big corporate hitter look after them. He is very much that – a very driven character."

According to the firm, Picon's decision to leave was motivated in part by family considerations, including the demands of a management role at a global firm that saw him spend more than half of his time away from his Madrid home.

DLA's co-CEO Simon Levine said: "I am disappointed, I understand that he had his personal reasons for doing it, but I hoped he could stay. However, I genuinely don't think it makes a big difference to the firm and its direction.

"The internal reaction has been very supportive. People have been shocked, many would have preferred him to stay but the majority of people have been very supportive.

"I can assure you that Juan and I remain good friends, we are close and our families are close."

In 2015, Picon was one of four candidates competing to succeed Knowles as CEO, running against then Italian managing partner Federico Sutti and current managing director of developing markets Andrew Darwin in addition to Levine, who was ultimately successful.

With the exit of Sutti to Dentons later that year, Picon's run for the senior partner post in March 2016 was unopposed.

"He was very much the preferred candidate – these things are done like the old selection of the leader of the Conservative Party; soundings and that sort of thing," one former partner says.

The perception of Levine and Picon from partners and former partners alike is that the pair have been a tight team who have been close to their US management counterparts.

"They were a team; they were the team who were going to replace Nigel Knowles in running the firm," says one former partner. "Simon got the CEO job and Juan got senior partner and was going to do it in a different way and be more of a co-CEO in terms of helping Simon," he adds.

Many believe Picon was the ideal person for his role. They describe him as a corporate rainmaker who was respected both inside and outside the firm; a charismatic leader with extensive management experience and, importantly, as someone who came from outside of the UK, who could represent the firm's widespread continental European offices in the London-based management team.

"It is a loss, because a firm needs to have strong executive leadership," says an ex-partner. "That does not just mean a manager but someone who understands clients. If you look at DLA really closely, who do they have with client clout? The way to progress at DLA is through management, so who has the client side?"

These thoughts are echoed by another: "Juan was seen as someone who had won his spurs lawyering and that is important in a firm like DLA. He is not talking in the abstract about how to look after the top clients – that is what he has done and, in any organisation, that gives you authority."

His key client relationships include banking giant Santander, Spanish multinational Abengoa and US private equity firm KKR.

However, Levine argues that he has a strong executive team around him that will mitigate Picon's departure.

"The senior partner role in a law firm is a role that is a governance position not an executive management position. If you look at the composition of our executive, we have a new generation of people from around the world. Our board is also mixed gender and international, with an average age in their 40s," he says.

While Picon's role will be filled in the interim by disputes partner Janet Legrand, the firm's senior elected board member, his exit is set to trigger an election at what one former partner describes as "a firm that is more political than anyone will ever tell you".

In addition, it also represents a blow to Levine's ongoing project to consolidate Knowles' efforts to turn the global giant into a more profitable and upmarket firm.

A former partner argues: "When you have one dominant individual who commands a lot of loyalty and that person moves on, it is a hard transition to make work, and Juan's departure will make it a great deal harder."