The Belgian powerhouse has scored three goals in as many games so far after impressing during the last campaign, and opponents are paying him particular attention as a result.
Guzan said: "I definitely think he's becoming a marked man. Whether he's getting enough protection or not I'll let you guys decide.
"When you are a top player, you know other teams are going to look at you, try to shut you down and limit your chances. That's what teams have been doing and they will do it in whatever way they will deem necessary.
"Christian is going to have to fight through it at times and as a team, we have to back him up.
"We are in this together and there's a lot of football to be played. We have to find a way to keep battling and fighting and he's a big part of it.
"He is a huge player on the pitch - his ability to find spaces and get chances is great. Not just him, but Gabby Agbonlahor and Andi Weimann as well. We have got a bunch of players who are good going forward.
"I think our attacking four or five players are some of the best in the league. People might disagree with that, but it's a credit to their hard work and ability to press on.
"Christian, people know what he's about, but people haven't stopped him and he's only going to get better."