Spurs are currently 17th in the Premier League table, two points above 18th-placed West Ham United as they fight against relegation in the final two league games.
Their battle is not helped by the fact that captain Romero will be absent for the remainder of the season after suffering a knee injury in the loss to Sunderland last month.
The Argentina international is a pivotal part of the side when fit but is also a loose cannon when it comes to discipline. Alderweireld, who was once a leader in the side, sent a message to 28-year-old as he prepares to return for next season.
“I think he’s an unbelievable player, in moments,” Alderweireld added. “For example, with the red cards, you don’t help your team. When your team needs you, you need to be the captain steering the ship, not putting it in more trouble. He’s a very good player, but he should have done better in some situations.
“For me, centre-backs are players you need to count on, to be flawless, not crazy. Win your battles, be secure, that’s the number one. Long balls, passes between the lines, of course, that’s a plus, but the basic is to be secure.
“A captain has to be aware not to — I don’t say he’s causing trouble — but not to be a risk to himself. I call them trustful leaders. You need to be a calm person.”
The Argentina star featured 23 times in the Premier League this season, with four goals and two red cards. Reports state he may have played his final game for the club, especially if they are relegated later this month.