"These are two really tough games for the players, but they can really put down a marker in them," said the Wales boss.
"Originally, I specifically wanted only the Czech game in September because it is not a time of year when we are traditionally at our best.
"As such, I preferred a single qualifying match, rather than a double-header, so that we could throw our entire focus into just that one game.
"Just think back to what I inherited in the last World Cup campaign when we were asked to play England and Poland in the space of four days in September.
"It was too much for the players and I don't really want that sort of thing happening again while I'm in charge.
"However, once Brazil got in touch with us and requested a game, it was extremely difficult to turn them down.
"It is a friendly, of course, rather than a competitive match with three points at stake, which helps.
"But, anyway, I couldn't really deny the players the opportunity to line up against the great Brazil, with the tradition and aura they bring to football.
"For some of our younger players, it will be a wonderful learning experience.
"In fact, to rub shoulders against the Brazilians will be a great thing for even our more experienced men.
"And if we can achieve a decent result in the Czech Republic and then do well against Brazil, it will do wonders for the stature and confidence of the players. It will be a big, little period for the team."
Toshack went on, "What I will emphasise to the players, however, is the need to channel their entire energies into the Czech game until it is out of the way.
"That is the one that counts in terms of qualifying points.
"I don't want them thinking about which Brazil shirt they are hoping to swap until we have played against, and hopefully earned a good result against, the Czechs.
"But once that one is over, Brazil will be a second enormous challenge and opportunity for them.
"The Brazilians have a new manager in Dunga after their failure in the World Cup and the star names will be looking to put down a marker to him against us.
"They really are a different bunch, these Brazilians. I managed a few of them myself in Spain. Bebeto, Rivaldo, Roberto Carlos, Mauro Silva - World Cup winners the lot of them. Great players, great characters, great to test yourself against.
"I fully expect the likes of Ronaldinho, Kaka and today's top Brazilian stars to line up against us.
"For our players to meet first the Czechs, and then the Brazilians, in the space of three days can be seen in one way as a hugely daunting challenge.
"But it is also one the players should relish because some of them can really make names for themselves in these games."