Rossi led the majority of the Sepang race on Sunday, but was being caught by Marc Marquez when he crashed at the first corner with four laps remaining.
Vinales, who ended Yamaha's 25-race winless run at Phillip Island the previous weekend, recovered from a lacklustre qualifying to finish fourth in Malaysia, despite losing time behind Alvaro Bautista's satellite Ducati early on.
But the Spaniard admitted that even without qualifying poorly - he started 11th - he could not achieve the pace Rossi and Marquez were setting at the head of the field.
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"If I could do low 2m00s [laps], maybe I could win the race, but today [that] was impossible," said Vinales.
"The track was so slippery, I was even struggling to do high 2m00s.
"With four laps to go, I didn't have grip on the tyres. I destroyed the tyres. But I'm happy we have consistency there.
"I think today I could not keep low 2m00s because it was so hot, and also I got stuck with Bautista and other riders, it was so difficult to overtake.
"My chance to get on the podium went away, but I'm happy I was pretty close to Alex [Rins] and Johann [Zarco] at the end. I did my best."
Vinales said he was not surprised to see Rossi command the majority of the race, and added the Italian's performance was another important boost for Yamaha.
"I always saw Valentino at the same distance [ahead of me], I think we were riding really good," recalled Vinales.
"Honestly, I was thinking he could win the race - he had nearly the same pace as me [in practice] and always in the race he gives a little bit more.
"It's great for Yamaha that in Phillip Island I was in front [and] here Valentino was in front [before his crash]. It's good for them to get confidence."
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