Action on the European 2-year-old front heats up on Sunday with the running of the first juvenile Group 1 of the season at the Curragh and the reappearance of the Aga Khan's precocious Siyouni at Maisons-Laffitte.\nThe $319,000 Phoenix Stakes has been won by Aidan O'Brien in nine of the last 11 years. On Sunday the master of Ballydoyle will send out four of the eight runners in the six-furlong dash, which has been taken in recent years by Mastercraftsman, Holy Roman Emperor, George Washington, and Johannesburg, all of them trained by O'Brien.\nBut it is Tommy Stack who will saddle Sunday's favorite in Walk on Bye, a filly by 1995 Phoenix winner Danehill Dancer out of a Group 1-winning mare by 1992 Phoenix winner Pips Pride. Walk on Bye was the 1 3/4-length winner of the Group 3 Anglesey Stakes at the Curragh on July 12 when she beat the Kevin Prendergast-trained King Ledley as well as Beethoven, one of O'Brien's Phoenix quartet. The only filly in the field, Walk on Bye will be ridden by Wayne Lordan.\nO'Brien will counter with a Danehill Dancer colt in Alfred Nobel, who won the Group 3 Railway Stakes at the Curragh on June 28 by 1 1/4 lengths over the maiden In Some Respect, who tries him again in the Phoenix. Alfred Nobel will be ridden by Johnny Murtagh.\nSiyouni rates top billing in the Group 2, $184,000 Prix Robert Papin, a 5 1/2-furlong contest at Maisons-Laffitte. By Pivotal out of a Danehill mare who is a half-sister to four-time Group 1 winner Slickly, Siyouni has won all three of his starts at five furlongs. Most recently he took the listed Prix La Fleche by three lengths at Maisons-Laffitte on June 17. Trainer Alain de Royer-Dupre will give Christophe Soumillon a leg up.\nThe big danger could be the Robert Collet-trained Dolled Up, a filly who was 1 1/2 lengths second to Siyouni in their mutual debut, but who improved to win the five-furlong, Group 3 Prix du Bois against colts at Chantilly last time. Italian invader Orpen Shadow made it 3 for 3 with a neck score in the six-furlong, Group 3 Premio Primi Passi at San Siro in Milan on \nJune 20, but the Robert Papin will be a step up in class for the Bruno Grizzetti-trained son of Orpen.