Jose Mourinho’s “defensive game” is to blame for Alexis Sanchez’s poor form and the Chilean should be concerned at how things are going, says former Chile youth national team manager Jose Sulantay.The 29-year-old was a marquee signing for the Red Devils during the January transfer window, with interest fended off from arch-rivals Manchester City to secure his signature.The former Barcelona and Arsenal star has, however, struggled to produce his best since arriving at Old Trafford, netting just three times in 22 appearances. Article continues below Editors’ Picks Man Utd ready to spend big on Sancho and Haaland in January Who is Marcus Thuram? Lilian’s son who is top of the Bundesliga with Borussia Monchengladbach Brazil, beware! Messi and Argentina out for revenge after Copa controversy Best player in MLS? Zlatan wasn’t even the best player in LA! He is yet to open his account for the current campaign, with United relying on others to see them through a slow start to the season.Sulantay, who previously worked with Sanchez within the Chile U20 set-up, feels Mourinho must be considered responsible for failing to bring the best out of a man who has starred elsewhere.He told El Mercurio ahead of United’s opening European fixture of the season against Young Boys on Wednesday: “Of course, the Champions League is an extra motivational factor for any footballer.“But Alexis’ present, I don’t know if it will be fixed just because a great league comes along. I notice him being unbalanced and quite negative.“It will be hard for him to return to his great level if he continues like this.“And well, there’s little help from Jose Mourinho’s defensive game, which is based on long balls, skipping the sector where he plays.“That should worry him. Hopefully the picture improves.”Sanchez managed 80 goals in 166 appearances during his time at Arsenal, while 141 outings for Barcelona delivered 47 efforts.United need him to rediscover that spark if they are to compete on multiple fronts this season.Romelu Lukaku has remained their go-to man for attacking inspiration in 2018-19, but the Belgian striker needs somebody else to help carry the load and Mourinho must find an answer to that poser.