"It's like with boxer, who needs to box someone good," Portal told Cycling Weekly.
"It shows that he just doesn't sit still, and that he tries to find the difficulties and challenges. Racing that's maybe a little harder, or different."
Froome began his 2013 and 2014 seasons in Oman, where he won the stage race overall both times. This year, he decided to ride in the Ruta del Sol in Andalusia, Spain.
He could not match the rapid accelerations of team Tinkoff-Saxo's Alberto Contador yesterday up the Alto de Hazallanas, but responded steadily to finish second at 19 seconds. They were well ahead of their other rivals, like Romain Bardet (AG2R La Mondiale) who placed third at 1-39 minutes.
The 2014 Giro d'Italia winner, Nairo Quintana (Movistar) was also due to race the Ruta del Sol, but pulled out after a crash at the Colombian championships.
Contador, who has more Grand Tour wins than any other current cyclist, provides Froome an ideal early season challenge ahead of July's Tour de France.
Only the 2014 Tour winner, Vincenzo Nibali (Astana) is missing from the Ruta start list. Instead of racing in Spain, the Italian is in the Middle East for the Tour of Oman.
Yesterday, Nibali lost 2-27 minutes to winner Rafael Valls (Lampre-Merida) on the Green Mountain stage, which Froome won last year. Froome's potential Tour helpers Wout Poels and Leopold König lost 1-27 and 2-37, respectively.
"In my opinion, the top guys need to race each other. Without Contador, Quintana and Nibali, it's too easy for him," Portal added.
"The top guys need the rivalry. The same for Contador, the same for everyone. Maybe it's nice for Nibali here without them."
Nibali said yesterday after Green Mountain that early season results "mean nothing" when looking ahead to the Tour de France.
All four riders are due to face each other in July at the Tour de France. Only Contador will race the Giro d'Italia beforehand.
The Italian Tirreno-Adriatico stage race in mid-March will offer the next test for Froome. He will again go up against Contador, but also Quintana and Nibali. First, he faces another summit finish today in Spain.
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