With Manchester United in the market for a new centre-forward this summer, most of those who have been mentioned as potential arrivals at Old Trafford can be split into two distinct categories. Young, talented yet somewhat-unproven-at-the-top-level,Rasmus Hojlund-style forwards, such as Brian Brobbey and Benjamin Sesko. Or, instead, those in their late-20s who may be approaching their last chance to secure a move to a bonafide European giant. An Ivan Toney or a Serhou Guirassy. Jonathan David, however, is one of the few who falls somewhat in the middle. At 24, the Lille frontman still yet to h…