The pair have both made an impact since their summer arrival.
"Robin has the experience of playing in Europe with Arsenal," said the Welshman, who became the first player to clock up 600 Premier League appearances at the weekend.
"The goals he has got will hopefully give us that extra edge this season.
"Shinji is that kind of player who will thrive in Europe, where possession is key.
"He keeps the ball and gets into positions where he is hard to pick up.
"I am sure they will both be very good additions in Europe for us."