Nelsen, however, has warned Elmer there's no first team guarantee.
"Obviously it will be up to Jonas to force his way into the team," Nelsen told reporters following training on Friday. "We need to have two guys at every position to provide competition. Nobody has a guaranteed position and everybody has to try and fight really hard in training to keep their spot. We want really healthy competition."
Elmer says he always fancied MLS after seeing David Beckham make the move.
"My agent in Switzerland told me that this club really needed a left back," Elmer told MLSsoccer.com. "That was one week ago and now I have just finished my first training session. That's how it works in football sometimes. It just happens very quickly.
"When David Beckham arrived here [back in 2007], you could see the video in Europe and see what a fantastic league it is here," Elmer added. "It just fascinated me and that's why I decided to come here."