Mark Webber believes that it is a "travesty" Fernando Alonso is battling at the back of the Formula 1 grid with McLaren in 2017, but thinks the Spaniard's market value has never been higher as he begins to plan for 2018.

Alonso has struggled towards the back of the field for much of his second stint with McLaren, linking up with the team in 2015 when it struck a power unit deal with Honda.

Honda's engines have lacked both reliability and performance through 2017, leaving McLaren at the foot of the constructors' championship with zero points from the opening seven races of the year.

Alonso is currently evaluating his movements for 2018, but ex-F1 racer Webber believes that his worth to possible teams is greater than ever.

"It's day-by-day with Fernando. He's his own man," Webber said at the FIA Sport Conference in Geneva when asked about Alonso's future.

"He's a phenomenal talent. It's a total waste and an absolute travesty that he's at the back of the grid, driving a car that's uncompetitive. But he's still in a situation where he's driving phenomenally.

"I think his market value has never been higher, what he's done at the Indy 500, and then what he's done sometimes with that McLaren. Stoffel [Vandoorne] I don't think knows what's hit him, so that's what it's like on Sundays working with someone like Fernando.

"I don't know. Let's see what engine McLaren get, see if they can hold him over the winter, and convince him that they're going to win next year."

Speaking about Alonso's Indy 500 adventure, Webber was full of praise for the two-time F1 champion, having also heard impressive stories from others about his display.

"Big balls for having a go, I must take my hat off to him," Webber said.

"I've been hearing incredible things about how awesome he was. Gil de Ferran, I know Gil well, and he just said it was phenomenal how well he took to it.

"I was happy he was in one piece, that was the biggest thing I was happy with."