(CNN) - "I am in charge of the workplace atmosphere," he said at a news conference.
Philbin said he was unaware of alleged misconduct by Richie Incognito against fellow offensive lineman Jonathan Martin until Martin's representatives informed the team Sunday evening.
"We immediately took those concerns very, very seriously," and informed NFL Commissioner Roger Goodell to request a review, Philbin said.
ESPN also reported that Martin never brought his concerns to Philbin.
But many who know the ins and outs of pro football say Philbin should have known what was going on in his ranks and taken action much sooner.
"The recent developments in the Jonathan Martin-Richie Incognito situation (have)shown us one thing: Joe Philbin is to blame for the turmoil in the Miami Dolphins' locker room," writes Gil Alcaraz of rantsports.com.
"First and foremost, an NFL head coach needs to know what's going on within his own locker room. If there's a player bullying another player, sending him threatening voice mails and text messages while making him feel uncomfortable on a daily basis, the head coach has to be aware of it."
The central allegation against Incognito involves messages to Martin, including a voice mail in which Incognito allegedly used racial slurs, threatened physical violence, and used the words, "I'll kill you." Martin's representatives have turned materials over to the NFL for an investigation.
Incognito allegedly also got Martin to contribute $15,000 to help finance a trip to Las Vegas by a group of Dolphins even though Martin preferred not to travel with them. Martin gave Incognito the money, fearing the consequences if he did not, ESPN reported.
Incognito, on Twitter, accused a news organization of "attaching my name to false speculation," but that tweet and others were later deleted, according to bleacherreport.com. Incognito has been suspended; Martin left the team. It's unclear what lies in store for either of them.
Incognito said Tuesday he is "weathering the storm right now."
Philbin "is ultimately to blame here," Dan Shanoff writes at USAToday. "... Philbin either actively neglected his team culture (his claim) or he knew and did nothing (which would be worse). Let's give him the benefit of the doubt -- at best, he is an appallingly ineffective leader."
The Sun Sentinel reports that Dolphins coaches had asked Incognito to toughen up Martin -- orders he may have taken too far. The report does not say whether Philbin himself made the request.
Philbin did tell players each year to "cut out" rookie hazing, the paper reports.
But how much are NFL coaches really expected to police their teams?
By and large, they "let their players, and especially their seasoned veterans, maintain harmony in the locker room," Ken Belson writes in the New York Times. "In the crudest sense, they are hired to build a winning team, and as long as players do their jobs well, what happens elsewhere is largely immaterial."
"To some extent, the inmates run the asylum," Trevor Pryce, a defensive end who spent 14 years in the NFL, told the Times. "The coaches have a lot of other things to deal with."
No organization speaks for all NFL coaches. The NFL Coaches Association "represents the interests of nearly 500 assistant coaches," according to the website of its executive director, David Cornwell. He was not immediately available Wednesday to discuss this issue.
Ricky Williams, who played with Incognito in Miami, said he believes a coach should only step in if behind-the-scenes behavior affects play on the field. "The locker room, we keep coaches out for a reason. It's our space," Williams told KGMZ-FM in San Francisco, according to NFL.com. There is "a lack of leadership in that locker room," he said of the Dolphins.
Some coaches have been credited with taking disturbing behavior seriously.
"Hall of Famer Bill Walsh's coaching tree never tolerated any form of hazing or harassing. Pete Carroll doesn't allow it in Seattle. Jimmy Johnson and Mike Shanahan have said they've never witnessed bullying to the extent that is alleged in this circumstance," NFL.com reports.
As the conflict between Incognito and Martin spirals into a time of reckoning for the entire NFL, league officials face the task of laying out in clear terms just what coaches are responsible for -- and how to punish coaches when their players cross the line.
Philbin has compared running a team to running a school. When his two children go to school each day, "I have certain expectations that the administration, the teachers and the staff are going to create a safe atmosphere where my children can learn and develop as people," he said at his news conference Monday.
"This is no different," he added. "I take this responsibility very seriously."
But even if Philbin shoulders blame for what allegedly transpired in his team, he's not alone, says columnist Jen Floyd Engel of foxsports.com. She points to others in the team's leadership and the players themselves. "(I)t is every person who saw what was happening to Martin and did nothing who deserve our condemnation."