No Dolph and John came on board around the same time. Woo had promised another pilot to Alliance Communications, with whom he had done the TV remake/pilot of ONCE A THIEF, and the head of Alliance suggested Dolph. It came together very quickly, it was announced in September 1997 and started shooting in November. Which is one of the reasons, Woo had very little to no time to rewrite and prep it (let alone film it: 3 weeks) not mentioning he was writing his own projects at night during the same time KING'S RANSOM and PHANTOM OF THE OPERA!
Of course during the 90's he always tried to "iconise" his lead actors closely to Chow Yun-Fat (especially since he was frustrated not to be able to work with him then). By the way, some of the action sequences are just pretty much lifted from his own lesser known films HEROES SHED NO TEARS and JUST HEROES.
BLACKJACK is too cheesy for its own good, but it sure features Dolph like you've never seen him filmed before and the best thing he's done in the late 90's when his career was its lowest...