Before the Los Angeles Dodgers pulled the trigger on their January trade to bring back catcher Russell Martin, they watched enough video to convince themselves he would bounce back from career lows in batting average and slugging percentage. ''Bringing Martin back, just him getting up to speed with our guys, the early returns have been unbelievable,'' said Andrew Friedman, Dodgers president of baseball operations. As a replacement for Yasmani Grandal, who signed as a free agent with Milwaukee, Martin is connecting with returning catcher Austin Barnes and eliminating concerns about the possibility of splitting time.