Champions Shamrock Rovers showed why they're still the team to beat after producing a stunning performance to easily defeat Derry City at the Ryan McBride Brandywell Stadium.First half goals from Richie Towell and Jack Byrne sealed the victory but in truth it was their overall display which showed their class as they dominated for the majority of the contest.In Byrne, they have the best player in the league and his individual performance demonstrated why Rovers were so desperate to keep their man from moving to the MLS.But Derry manager Ruaidhri Higgins will be disappointed that his players failed to turn up on the big stage and it will be a case of going back to the drawing board.An interested spectator at the game was Republic of Ireland international James McClean, who was back supporting his former club. As it happened: Derry City 0-2 Shamrock Rovers City had the first real chance on seven minutes as Ryan Graydon's clipped right wing cross found Michael Duffy at the back post, but after rising well his header down flashed just wide.Rovers started to up the ante with Byrne in particular running things from midfield and they went close on 14 minutes as Towell's flick was cleared away by Shane McEleney.The visitors deservedly broke the deadlock on 30 minutes in spectacular style as Byrne's delishes cross field pass found Trevor Clarke and the left wing back's header found Towell, who burst into the box to volley the ball over City keeper Brian Maher.Right on the stroke of half-time Byrne's quick thinking a goalkeeping error by Maher resulted in Rovers doubling their lead.The City shot-stopper raced out of his goal to clear the ball close to the left hand side-line, Gary O'Neill flicked the loose ball into the centre