Barca romped to a fourth Primera Division title in five years last season but Fontas feels his former club have taken another step forward this term under Martino.
And Barca's results so far certainly bear testimony to that, with the Catalan giants still unbeaten under Martino and leading La Liga with 28 points from a possible 30 heading into Tuesday's trip to Celta.
They have also picked up seven points from nine in the Champions League, lifted the Spanish Super Copa and on Saturday downed arch rivals Real Madrid 2-1 in the first Clasico of the season.
An impressed Fontas, who left Barca for Celta this summer, told reporters: "I think the new coach has incorporated some new things which Barca didn't have before, which makes them more dangerous.
"They are a very dangerous team who are less predictable than in previous years."
Celta go into the match just a point above the relegation zone but with confidence renewed following their shock 5-0 mauling of Malaga on Saturday.
Celta had taken just two points from seven league matches prior to their trip to La Rosaleda but a brace from Alex Lopez plus further goals from Augusto Fernandez, Nolito and Charles earned them a huge win.
Fontas admits that victory was a huge boost but knows they cannot allow themselves to bask in the glory for long as they prepare to face the champions.
"We all needed the game in La Rosaleda, as much the team as the fans. This win has lifted morale and helps us believe in what we're doing," he said.
"But now we need to forget that 5-0 and think about Barca, a difficult opponent, the league leaders, and try to surprise them.
"We have nothing to lose and a lot to gain."
Barca's win over Real on Saturday kept them one point above Atletico Madrid at the top of the table, and moved them six clear of Carlo Ancelotti's men.
Like Celta though, Barca are well aware they now need to put that success behind them and focus on their upcoming matches, which after Tuesday's game sees them face local rivals Espanyol on Friday and host AC Milan in Europe next week.
Midfielder Andres Iniesta told Barca TV: "At this stage of the season nothing is decided and there's still a long way to go.
"It's true that these types of games (Clasicos) give you a boost, an extra motivation, but on Tuesday we're back playing for another three points and if we don't win that game then what we did against Madrid won't count for as much."