Chelsea happy to rotate goalkeepers, says Rosenior
The English manager brought in Denmark's Filip Jorgensen for the 4-1 victory at Aston Villa days after Sanchez, who has been first choice this season, struggled in a defeat against Premier League leaders Arsenal.
Rosenior was asked on the eve of Chelsea's FA Cup tie against second-tier Wrexham to explain his goalkeeping policy.
"For me, genuinely, I look at the goalkeeper position maybe differently for each game," he said. "I want there to be competition in every area of the pitch.
"I know traditionally if there's a change of goalkeeper it's like 'He's now the number one'. It's not the case, it's not the case at all.
"So we will try and pick the best team possible for each game."
Rosenior played down potential fears over rhythm and confidence.
"You need continuity, but you need to win games of football," he said. "There's different ways, modern coaching or old school or anything.
"I will pick the team I think is best to win each game. I don't think I've kept the same 11 in any game that we've played.
"Now, people can say we need continuity, and if we lose then we don't have enough continuity. If we win then it's the right decision."
Rosenior, who took charge at Stamford Bridge in January, said Spain's Sanchez had reacted well to being dropped.
"I've spoken about (winger Alejandro) Garnacho and the way he's responded to not being in the team," he said.
"If we're going to be successful, I'm sure in the short and long term you need a group, you need a squad with the right mentality and Rob so far has been absolutely magnificent in that."
Rosenior said he was expecting a tough battle in Saturday's fifth-round tie at Hollywood-backed Wrexham, who have enjoyed three successive promotions and are now in a Championship play-off spot.
"When you see a club grow, develop, improve and come up through the leagues, it's a great story," said the Chelsea boss as he paid tribute to Wrexham counterpart Phil Parkinson.
"They've done a great job, I think Phil's done an incredible job...We know it's going to be a really difficult game. It's a club that's on the rise and there's a good energy in them."