USMNT fans held their breath during the second-half of the squad’s opening game of the World Cup.The US kicked off their World Cup campaign in style on Friday night, with a history-making 4-1 win over Paraguay.USMNT got their World Cup campaign off to a perfect start with a 4-1 win over ParaguayGettyThe three-goal margin of victory was the United States’ largest at a World Cup since the inaugural tournament in 1930.Folarin Balogun scored twice in the first half to become the first American with two goals in a World Cup fixture.Despite Mauricio pulling one back for Paraguay, Giovanni Reyna’s late strike added some shine to a magnificent display by the co-hosts.For the 70,492 fans at SoFi Stadium, it was a dream start to the tournament.However, in arguably the only thing that went sideways, their star midfielder Christian Pulisic was substituted at half time.Christian Pulisic subbed off with a calf injuryPulisic was dynamic through the first half, spearing through the Paraguay defense to force an own goal for USMNT’s first.He would then set up Balogun for the team’s second – but as the teams took to the field for the second half, Sebastian Berhalter came on for Pulisic.“That’s not a tactical substitution,” Fox pundit Stu Holden remarked during co-commentary duties. “For your star player, something has to be up.”Pulisic’s first-half performance outstanding enough to earn a player rating of 9/10.After the match, Pulisic told reporters that he was kicked in the back of his left calf, and the substitution was more of a precautionary move.Ben Jacobs rated USMNT’s players after a World Cup opening wintalksportPulisic was subbed off at half-time in USMNT’s winGetty“I just got a bit of a kick first half, so I’m really hoping that it’s nothing,” Pulisic said, via ESPN.“Taking a little bit of precaution today, but I’m hoping I’ll be fine the next few days.“Just the back of my leg, my calf area. But I’ve had similar things before and I’m staying positive. I don’t think it’s anything at all.”Will Pulisic be fit for USMNT’s next World Cup fixtureDespite echoing Pulisic’s precautionary comments, USMNT’s manager revealed that the star midfielder was struggling to walk during the half time interval.“When it [Pulisic’s body] start to get cold, he cannot walk,” Pochettino told reporters, also revealing that the substitution was a “last minute” decision.Pochettino said Pulisic was struggling to walk, and the substitution was precautionaryGettyWorld Cup WhatsAppDon't miss an update from talkSPORT in our dedicated World Cup WhatsApp channel.Search for ‘talkSPORT World Cup’ in your ‘Updates’ tab on WhatsApp and we’ll drop the proper, unfiltered football chat straight to your lock screen—no fluff, just pure talkSPORT energy.It’s where you’ll find out all the new rules to watch out for, England and Scotland reaction and big match player ratings. Plus there will be loads of debates on the biggest talking points as Haaland, Mbappe, Kane and the biggest names in football descend on America, Canada and Mexico.Fox did report that Pulisic had motioned to his family and friends in the crowd: “I’m good”.Pulisic has a full week to prepare for USMNT’s next World Cup fixture, which will be against Australia in Seattle on June 19.Stay up to date on all things USMNT across our talkSPORT platforms – subscribe to our YouTube channel for the latest news, opinion, exclusive interviews and our daily unfiltered, unscripted show ‘The S* Word, from 8am ET.