"I knew it would be a very complicated and difficult game. They caught us on the break in the first half and then shut up at the back and it was tremendously difficult for us to break through," Aragones told a news conference.
"But the introduction of Cesc in midfield helped give us more touch, Joaquin gave us more width on the right and Raul got the vital breakthrough with his goal."
Tunisia had taken a shock lead in the eighth minute through midfielder Joahar Mnari and although Spain dominated for much of the game it took them until the 71st minute to equalise when Raul slid in his rebound from a shot by Fabregas.
Both players come on at halftime and were joined by winger Joaquin 10 minutes later.
Spain's Fernando Torres sealed the win with two late goals, the second from the penalty spot, making him the leading scorer in the World Cup with three.
"Their first goal upset us and we were a bit nervous," said Aragones. "We're a young side and we dropped our usual game and tried to play long balls.
"But in the second half we had a team with more touch and we were able to make more ground on the wings and then did more damage," he added.
"After Cesc (Fabregas) took a shot and Raul got the goal, it became much easier to open them up. Their contribution was extraordinary."
"It was harder than we expected but it is important to win any way you can. Today the team showed spirit and did not get downhearted when they were behind," Torres told reporters.
"As long as the strikers keep scoring we will progress in this tournament. It's nice to be the top scorer but I only score goals to help the team.
"I hope I can score even more to take the team a long way in this competition."
Tunisia were left to bemoan the three late goals which killed off their hopes of an upset win.
"I'm very disappointed, especially for the team and for Tunisia because we had good tactics," said Tunisia's French coach Roger Lemerre.
"We were concentrating on their attacking game, but it all crumbled because of a single mistake," he added referring to Raul's equaliser.
"All is not lost but we didn't win anything here either. The Ukraine game (on Friday) will be decisive, the route will be difficult, but we still have hope."