McLaren are yet to make a decision over a replacement for Fernando Alonso for the Monaco Grand Prix after the Spanish driver was confirmed to race in the Indy 500. The two-time Formula One world champion will compete for the Andretti Autosport-run McLaren team in the endurance event on 28 May – ruling him out of competing in F1's blue-ribbon race in the principality.

While the decision keeps alive Alonso's hopes of completing the motor sport triple crown of the Monaco Grand Prix, Indy 500 and Le Mans 24 hour race, it has sparked speculation over who will fill the vacant seat with the British team for next month's race. Jenson Button has a contract with the team until the end of 2018 after initially opting to taking a sabbatical then deciding to end his career in the sport.

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Alternatively, one of McLaren's test and development drivers could be enlisted for the role. In February, Briton Lando Norris joined established reserve racers Oliver Turvey, Nobuharu Matsushita and Nyck de Vries and any of the quartet could be drafted in to partner the Belgian Stoffel Vandoorne.

The leading candidate is likely to become clear during a two-day mid-season test after the Bahrain Grand Prix when Alonso's prospective replacement could be given a much-needed run-out.

"Fernando's replacement driver is not in place," executive director Zak Brown said. "Those conversations are ongoing, we have a few different options, we will state who that is when we know.

"Eric [Boullier, team manager], who runs the F1 team, is ultimately responsible for making the recommendation as to what driver should go in the car and I think he will be here at the weekend so I can save questions for him. He is working on it. I wouldn't want to share the conversations he has had with whom."

The decision taken by Alonso has come amid a wretched second spell with McLaren which has yielded just 65 world championship points, without a single race victory or pole position. The 2017 campaign has started in similarly ignominious fashion, with retirements in the opening two races in Australia and China.

Fernando Alonso
Eric Boullier (right) will make the decision over who will replace the absent Alonso Reuters

Such performances have led to speculation the 35-year-old – who was approached by Mercedes to replace Nico Rosberg in the off-season – could cut short his contract with McLaren, which expires at the end of the current season. Brown has played down the significance of Alonso's brief absence and says the Woking-based team will use it as an opportunity.

"I would love to have Fernando to be in two places at one time but we can't, at least that technology has not yet been developed," Brown said. "I think the opportunity for the prize in Indianapolis is very large and an opportunity that none of us want to miss.

"As Fernando has said – whoever we end up putting in the car, Stoffel is doing an outstanding job, so we will expect whatever the car is capable of, Stoffel to be able to achieve that. As will whoever the co-driver is.

"We have to look at bigger picture and the entirety of what McLaren-Honda is trying to achieve, for the sacrifice of not having Fernando in Monaco but having him in Indy. When we step back and look at the season, we will say that was the right decision."