Hernandez joined Hart, Pablo Zabaleta and Marko Arnautovic in making the move to the London Stadium earlier this week, arriving for a £16m fee on a three-year deal which sees him become the club's highest earner of all time.
The Mexico international's previous spell in England saw him develop a reputation as a prolific goalscorer at Manchester United, although many of his appearances came off the bench and Hart believes that he will want to show that he is capable of being a starting striker.
"He's a finisher. Sir Alex Ferguson over the years was a genius at having players like that and using them at the right time in pursuit of winning titles," Hart told Sky Sports News.
"He probably felt he should have had more game time, but you have to balance that with some of the players that United have had over the years.
"He went to Real Madrid and then Leverkusen, still scoring goals in the Champions League and still showing what a top player he is. Now is his time to come back to the Premier League and show he should be a number one striker."
Hernandez's competitive debut for the club could come against former side Manchester United at Old Trafford on the opening day of the season.