Jenson Button says Stoffel Vandoorne could have equalled his own impressive FP2 time were it not for a sloppy first sector in Bahrain.
The highly-rated Vandoorne has replaced Fernando Alonso this weekend after the Spaniard failed an FIA medical on Thursday. In his first practice sessions he finished 18th in FP1 before improving to 11th in the evening session.
He was eight tenths down on Button's own impressive time under the lights which saw the 2009 champion finish as best of the rest behind Mercedes, prompting him to target a place in Q3 on Saturday. Button thinks Vandoorne would have been much closer had he hooked up a better lap on the super-softs.
"It's always a challenge stepping up to Formula One," Button said. "When you've raced in GP2 for a couple of years it's nowhere near as big a step as it is from other categories, from ten years ago it's much closer. I'm sure there are corners here that are much faster [in GP2] than Formula One cars!
"He's done a really good job today and he is quick. If he'd got his first sector together he would have been very quick - second sector was the same time as mine, third sector pretty much the same. He'll be quick. It's good for him and he's doing what the team expected from him."
Vandoorne only knew he was replacing Alonso on Thursday and flew in from a Super Formula test in Japan in order to be in Bahrain for practice, where he was due to fly later this weekend in his capacity as reserve driver. He says he feels fully prepared despite his late start to the weekend.
"I got the call yesterday evening when I was about to leave Japan and from then on things started to get a little bit hectic," Vandoorne said. "I had a lot of calls with all of the McLaren engineers, they sent me through all the files. I had to know all the information about the steering wheel, operationally before the grand prix - during the race, It's what we can say, not say, what we have to do so yeah, I've spent my time well on the plane and I think today went very well and after a night's sleep thinking about tomorrow I feel very confident about it."