Manchester United strikers Marcus Rashford and Anthony Martial should be looking at scoring “20 league goals at a minimum” this season if the club is to challenge in the top four, according to pundit Stan Collymore.The Red Devils struggled to sixth last season in the Premier League, following a mixed campaign that saw Ole Gunnar Solskjaer succeed Jose Mourinho as manager at Old Trafford.United have made only a clutch of additions to their squad for the new season, too, leading some critics to dismiss their chances of a return to the Champions League qualification places as a fantasy. Article continues below Editors’ Picks What is Manchester United’s ownership situation and how would Kevin Glazer’s sale of shares affect the club? Ox-rated! Dream night in Genk for Liverpool ace after injury nightmare Messi a man for all Champions League seasons – but will this really be Barcelona’s? Are Chelsea this season’s Ajax? Super-subs Batshuayi & Pulisic show Blues can dare to dream But an opening weekend 4-0 rout of rivals Chelsea looks to have breathed new life into their ambitions of challenging at the top this year, alongside title holders and cross-city rivals Manchester City and European champions Liverpool.Writing in his column in the Mirror, former Nottingham Forest and Liverpool man Collymore stated that United’s impressive display may hint at surprises to come, but that he believes key strikers Rashford and Martial need to emulate the efforts of City star Raheem Sterling in front of goal if they are to deliver.”I had Ole Gunnar Solskjaer’s boys missing out on the top four before a ball had been kicked this season,” he wrote.”But their start – a thumping 4-0 win over Chelsea, along with the performances of Paul Pogba, Marcus Rashford, Anthony Martial and Harry Maguire in particular – did hint that they might just surprise one or two of us.”I’m not going to get carried away by one result and say they are now nailed on for the top four. The game against Wolves will be a bellwether to all of that.”Success or failure for United this season will depend on their big characters – Pogba, Maguire and De Gea. But also to a certain extent on Rashford and Martial.”A couple of seasons ago I wrote that Manchester City’s England forward Raheem Sterling needed to start producing the sort of football we knew he was capable of far more consistently.”Now it’s time to send the same message to the United frontmen. Manager Solskjaer is looking for players he can put his money on, players he knows he can rely on, and those two need to step up to the plate.”They will be full of confidence after their goals against Chelsea last weekend and I want to see both of them going north of 15 goals.”Last season in the league it was 10 apiece – and that’s not going to help United get to the sort of areas in the table they really should be.”Ideally, both should be looking at 20 league goals as a minimum in a 38-game season, which is the benchmark for all top strikers.”United travel to Molineux on Monday as they look to make it successive victories to kick off the new Premier League season. Check out Goal’s Premier League 2019-20 fantasy football podcast for game tips, debate and rivalries.