The young striker swung in a flawless cross that found Rooney in a surprising amount of his space and the veteran used all his experience to send the ball back across the 'keeper to send Everton into the dressing room a goal to the good.
Niasse spent the second-half of last season on loan from Everton at Hull City, scoring a spurt of goals despite the Tigers eventual relegation down to the Championship.
McCarthy, who has been linked with a move away from Everton, sat out the final pre-season friendly against Sevilla on Sunday with Koeman insisting the former Wigan player wasn't fit.
Everton host Stoke on Saturday to kick off their league campaign before also hosting Hajduk Split in their Europa League play-off next Thursday. And winger Aaron Lennon will be a game-time decision due to a minor knock suffered in training this week. They lost Marko Arnautovic, however, so they might miss the Austrian playmaker. The Potters finished with only four wins, five draws and 10 losses on the road. "We can improve and spend money but everyone can improve is spending money".
Everton 1-0 Stoke City: Rooney rescues the Blues
Stoke have been steady in the market and have remained in a stable position. This should make things too hard for Stoke City.
A revitalised Wayne Rooney is relishing a new lease of life at Goodison Park after scoring the victor in Everton's 1-0 victory over Stoke City in their opening Premier League game of the season.
We will have all the action and reaction as the two teams go head to head.
If the Toffees can become more secure at the back this season then a top-six finish will surely be in reach, with the supporters clearly believing that Keane will be a crucial man in the club's hopes of a successful campaign - here are the best tweets.