Alves crossed from Dutch club Heerenveen in January but has managed just three goals for 'Boro but Southgate has backed his man, saying goals will come.
"He's just got to keep working hard on the training field and do the things that have got him the goals in the past," said Southgate.
"I thought his head dropped a little bit and it was probably the right thing to bring him off.
"It's a very different league for him and a very different challenge. It's physically much tougher and Bolton are a strong, physical team."