Arsenal newcomer Shkodran Mustafi has said fellow new arrival Lucas Perez will be a tough proposition for Premier League defenders.
Former Valencia centre-back Mustafi and ex-Deportivo striker Perez took part in their first training session with Gunners teammates at London Colney after joining in the final days of the transfer window.
Mustafi already knows what to expect from his former La Liga opponent, telling the official Arsenal website: "He is uncomfortable to play against.
"He's a good striker -- he has everything a striker needs. He's someone you can play well with. He doesn't just run around and wait for someone to give him a pass to score a goal. He works a lot for the team as well and he creates chances.
"He's in the right place at the right time, as he showed last year in La Liga. I played there for two years and I know it's not that easy to score many goals in La Liga because you have great defenders there. I think he's going to help the team a lot."
Mustafi added he was confident that his own switch to the Premier League would prove a success, having taken advice from Germany teammate Mesut Ozil.
"We were at the European Championship and we had time to speak. He [Ozil] told me about the club, about the team, and the things that he told me made me come here,'' Mustafi added.
"I noticed that it's a club where I can develop, where I can grow as a player.
"He said that he's happy here, that the people are crazy for football and that it's a team that enjoys playing football the way that he does, the way that I do.''
Mustafi returned from international duty with Germany together with Ozil, while Lucas has been spending the past few days in London getting used to his new surroundings.
The club posted pictures on their website showing the pair taking part in training drills in front of Arsene Wenger.
Alex Iwobi also took part in full training after suffering a thigh strain in Arsenal's first match of the season, indicating that he would be available for Saturday's home game against Southampton.
However, Aaron Ramsey was not shown in any of the pictures, with the Daily Telegraph reporting that his return from a hamstring problem could be delayed.
Information from the Press Association was used in this report.