The home run derby has ZERO chance of screwing up Vladimir Guerrero Jr. ... so says MLB legend Jason Giambi, who tells TMZ Sports the rookie phenom should do it with no worries!!!
"They're a lot of fun," Giambi says.
Of course, Vlad has reportedly agreed behind the scenes to take hacks in the MLB's home run contest next month ... but nothing's been made official yet.
Some in the baseball world are hoping the 20-year-old will reconsider ... because the derby has been known to lead to players' slumps and even injury.