Nigeria coach Gernot Rohr said that Kelechi Iheanacho has changed his attitude to training and he is now working hard during sessions with the coaching staff.
Before the Super Eagles' win over Seychelles in March, Iheanacho was not one of the invited players, and was criticised by Rohr for not taking training seriously.
At club level, the Leicester City attacker was limited to a bench role in the Premier League, where he made 21 substitute appearances in 30 games for the Foxes.
After a couple of training sessions ahead of the Africa Cup of Nations later this month, Rohr assessed Iheanacho's attitude to work but disclosed that he still lacks confidence during Thursday's press conference.
"Kelechi Iheanacho changed, he's now much more quiet. He's working seriously but he's lacking confidence because he didn't play so much,'' Rohr told the media.
''I see that he's not happy but we want to make him happy, but we cannot give the players gifts, there's competition.
''We have a lot of wingers, we also have good center forwards now, we have three, so really we are lucky to have all these good players because the other countries are searching for strikers.''
On Wednesday, Rohr stated that Iheanacho is among the players that will play against Zimbabwe on Saturday at Stephen Keshi Stadium to improve match fitness.
The gaffer is expected to release his final 23-man squad for Afcon after the match, before they fly out to Egypt where they will play Senegal in another friendly match on June 16.
The Super Eagles will commence their hunt for a fourth Afcon title in Group B against Burundi on June 22.
They will play Guinea on June 26 and Madagascar on June 30.