The 32-year-old has joined the team after eight seasons at Ferrari and set the fastest time during pre-season testing in Bahrain.
"He is superb," Symonds told AUTOSPORT when asked about Massa.
"I didn't know exactly what to expect because I didn't know him particularly well before he joined Williams, but he is great.
"He is very quick, which we knew and he provides good concise feedback without any airs and graces, it's just 'this is what's happening'."
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Symonds is also impressed with Massa's dedication, with both the Brazilian and team-mate Valtteri Bottas staying at the circuit during days on which they were not running.
He believes that Massa can be a key player in the revival of Williams after a difficult 2013 season.
"He's a fabulous team player and such a charming person," said Symonds. "He was there every day we were testing, even when he wasn't driving, as was Valtteri.
"They are both working hard and wanting to push things forward.
"Felipe is just part of the regeneration of the team believing in itself again."
Symonds added that Massa's hunger for success, even after so long in F1, has also struck him.
"I noticed that when we first spoke to him, that he was hungry," said Symonds.
"He has got unfinished business and he will thoroughly enjoy trying to finish some of that off."
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