Sehwag smashed a run-a-ball 117 to put India in the driver's seat on day one of the first Test against England.
"'See the ball, hit the ball' - that is not quite the attitude of Test cricket. It is a wrong thing he was looking to do. Now, he played himself in, you have got to spend time in the middle," Gavaskar said.
Gavaskar was disappointed that Sehwag could not go on to score a double hundred.
"He was pretty determined, putting his head down. It's a pity that he was not able to make a double century. That would have taken a way the game from England.
"I am disappointed, even he will be disappointed. When one gets to a century after a long time, one always likes to go on. But he has done his job. It is just a personal disappointment.
"That he has scored a century after so long means we can expect him to make a few more in not just this series but also in the season ahead," Gavaskar told a news channel.
The last time Sehwag had scored a Test century was against South Africa in November 2010.
Apart from Sehwag, Cheteshwar Pujara was the other Indian batsman to impress at the Sardar Patel stadium, remaining unbeaten on 98 at stumps.
"We all know that he has got a very good temperament. We saw that when he scored that 70 against Australia before scoring a hundred against New Zealand.
"But the real test for both batsman and bowler comes overseas and that's where he will have to show whether he is an able replacement for Rahul Dravid," Gavaskar said.
About Tendulkar getting out for a low score, Gavaskar said "it's not a cause for concern".
The former captain advised the Indian bowlers to hit the right length and not be afraid of giving the ball air.
"It's going to slow down. With the second new ball, we saw that the ball was rarely going beyond the knee. If they hit the right length India might win the match in four days. They should not be afraid of tossing the ball around, that's when you can get the batsman to commit on the front foot."
He added, "India should look to score another 100-150 runs."
He said the solid platform laid by the opening duo of Sehwag and Gautam Gambhir gave India the advantage.
"If the openers set a good platform, batting becomes easier. That is why India is in such a sound position."