Mika Hakkinen has been giving his views to BBC Radio about the results from Jerez testing.
The former McLaren driver who was managed by Didier Coton - who joined Hamilton's management team last year - thinks that he's seen enough already.
"I have a strong feeling McLaren is in top form this year," said Mika, "like we saw in testing in Jerez, the Mercedes was not exactly up to the speed I expected them to be, so I don't see them competing too much this year."
This, from a former Mercedes DTM driver.
The evidence that Hamilton is going to struggle against his former team was put forward by Lewis himself; he reckoned that the Mercedes W04 lacked the downforce of his 2012 McLaren, let alone the new one. It will have been an added disappointment seeing as the Mercedes team were free to concentrate on their 2013 car a lot earlier than the other top teams.
After he'd managed to get some serious running in the car on Day Four Lewis was choosing his words carefully. "We have some work to do but it doesn't feel like it was a disaster. I feel like it's a good platform, a good foundation to work from."
"Definitely we are going to keep asking for downforce, and hope the guys continue to do a great job at the factory."
On the other hand, the running from Jerez made his old team look like they might have gone from strength to strength. Jenson Button proved last week that the 2013 McLaren looks even faster than the 2012 MP4-27. Setting a 1:18.8 second lap (almost a second faster than anyone else on Day One) on hard tyres and on a track not yet rubbered in was described by Felipe Massa as an "incredible lap". On that basis it doesn't look like they are going to have to worry about getting their tyres up to temperature.
The team were careful not to put in any more superfast laps over the week and mingled with the rest of the pack in terms of lap time. Although it was a strong hint that McLaren are going to be quick in Melbourne they don't want to prove it beyond all doubt so that the other teams start borrowing their designs.
It will be harder to disguise their speed at Barcelona.
Should the McLaren prove to be the fastest car of the opening grands prix then the irony won't be lost on Lewis Hamilton. Ever since 2008 he has been on at them to produce a Championship winning car. Then, the second he leaves, they do.
When Lewis signed for Merecedes, no-one thought that he would be challenging Vettel and Alonso for the Drivers' title - more, that he would be scoring the odd GP win whilst dragging the team into the position that Lotus occupied last year. It would be a double whammy if Mercedes fell short of even that aspiration (where they were a couple of years ago) whilst McLaren produced an unbeatable machine.
We are only 33% through the testing days and there's a lot of aero to be added and a lot of reliability to be found out. As we saw last season from McLaren, having a quick car doesn't count for anything if your fuel pump gets unhappy after an hour's use. But for those F1 fans who don't like Lewis Hamilton, the short amount of running at Jerez has given us a hint that there is the possibility that he has left McLaren at the wrong time.