Wilshere was left on the bench in Portugal for the 1-0 win on Friday, with Pearce suggesting the 18-year-old had "taken his eye off the ball" after he was arrested and bailed in the wake of a late-night fracas in Kensington.
Pearce, though, maintains the young midfielder - who made his senior international debut as a late substitute in last month's friendly against Hungary at Wembley - is now back on his game.
However, the former England defender insisted there were no guarantees in terms of team selection at Colchester's Weston Homes Community Stadium, for a match his youngsters must win to stand any chance of making the play-offs.
"Jack has been exactly the same as all the other players who weren't involved in Portugal - fantastic. His attitude has been very good," said Pearce ahead of Tuesday night's crucial European Championship qualifier against Lithuania.
"I have seen a touch more focus.
"Leading into the Portugal game, he was swapping phone calls with his agent and one to two other people in regards to newspaper articles which were going on.
"We just did not feel it was right to start him in Portugal.
"Since then, we think his focus has been much better.
"It is difficult for a young man, there are a lot of pressures on young players at the best of times.
"It is my job to read those situations as best I can."
Pearce continued: "I will let them all know what the team is tomorrow and there will be seven or so who are not in the starting line-up who will be disappointed.
"But one thing I can guarantee and it has happened for three years now, they will support the players in the team and when their chance does come, they will take it."
Former Nottingham Forest left-back Pearce feels managers have to be more than just coaches.
"There has never been any difference in football - managers have to be available all the time for the players," he said.
"At times, managers have to be sympathetic, they have to be stern at times and make tough decisions.
"The players' wellbeing is vitally important.
"But as long as there is a fairness in the players eyes about what we are trying to achieve collectively - the team is much more important than the individual, that has been, and always will be the case."
England manager Fabio Capello has a somewhat similar issue over star striker Wayne Rooney, who has been the subject of intense tabloid scrutiny ahead of tomorrow's Euro 2012 qualifier in Switzerland.
Rooney has travelled with the rest of the squad to Basle, but it remains to be seen whether the Manchester United forward starts at St Jakob Park.
"Fabio will judge that, and he has been in the game a long, long time," said Pearce, who works closely with the Italian.
"One thing you do know is you have to make sure individual players have got a focus and it will not detract from their performance.
"If in your own mind it is clear that will be the case, you select the likes of Wayne Rooney, who is an outstanding talent.
"If you feel it won't and someone else is pushing for a place, then you put them in."