The 29-year-old striker enjoyed a dream start to life at St Mary's after moving from Feyenoord in a reported Â£9million summer deal.
Pelle scored nine goals in his first 12 matches for Saints in all competitions and netted the winner on his debut for Italy.
The goals have dried up of late, though, and he was replaced in the starting line-up by Shane Long in Sunday's 1-1 draw at Chelsea.
Pelle ran straight down the tunnel at the final whistle, having played the final few minutes, and Koeman hopes the striker can end his three-month wait for a Premier League goal when Burnley visit this weekend.
"There has been a little bit of a reaction, yes, because nobody is happy to stay on the bench," the Saints boss said.
"Sometimes you need a reaction off the player in that situation
He is doing well.
"In that game, in that moment, I think it was good to change the way of playing with more fast players up front
Saturday we play at home."
Koeman has no fresh injury worries to contend with against Burnley, with Eljero Elia coming back into contention after missing last week's match through injury.
Sean Dyche's relegation-threatened side head to St Mary's buoyed by last weekend's shock win over champions Manchester City and having overcome Southampton 1-0 earlier in the season.
"Yeah, they beat us but it wasn't a very good game that day and we missed a penalty," Koeman said.
"It was a stupid goal against us but, of course, we analyse always the opponent and we play 11 against 11 and then one team is playing like Burnley.
"Sometimes it is difficult to prepare a training session for the match, but we expect an aggressive opponent who will press us with direct play.
"That is always difficult because they don't give you time to play and you have to that and you have to prepare for that."
Saturday's match will be their last before a two-week international break, during which time many of Southampton's players will be away with their national teams.
England duo Nathaniel Clyne and Fraser Forster are amongst those players, with some eyebrows raised by the fact left-back Ryan Bertrand did not join them in Roy Hodgson's squad.
"I am not surprised," Koeman said
"He had suspension for three games
After that he came back and is playing well.
"I think he played very well against Chelsea but I am not surprised because his time will come if he keeps working like this, keeps playing like this."
Meanwhile, Koeman downplayed speculation linking Southampton with a loan move for talented Real Madrid teenager Martin Odegaard.
"It is not my job to do scouting of young players," he said of the 16-year-old Norwegian midfielder.
"He moved to Real Madrid - that means that he is a very good player."
Source : PA